Personally, building is one of my biggest dilemmas when trying to play the game more "seriously" and with that I'm referring to: playing without cheating or/and not making everything simple as possible for you Most simmers who read my other threads probably know that I love huge hoods, where everything is "custom made", i.e. I don't like downloading them, so this project usually get a bit tedious, especially now that I plan to build everything from scratch (due several lots crashing the hood when browsing the lot bin). Because this is a time consuming project (due to personal medical issues in real life, I've got a lot of free-time) and building lots is one of my "enemy" areas of the game, I often end up building one lot that I took alot of time doing and then get an urge to quit the game due to getting overwhelming to repeat this over and over again and don't feel I get any playing interests to actually play the game. But the reason I started this thread is because of two issues:

BUDGET/FUNDS. I don't like to cheat with a sims funds other than their starting funds (no 20K handouts also) I calculate based on various factor such as their role in the hood and their economy so each family has very limited funds. Like for example, SPOILER: While loans and mortgages tends to solve this dilemma, and can make sense for a basic unfurnished house (walls, floors, windows etc), Normally WHO would take a huge loan for sake of wanting an expensive painting or sofa? (Unfortunately you can't pay them build/buy mode objects off slowly as in real life and personally I'm not a big fan of "pay later"/having bets methods and save everything "extra" up.).
Which leads to the second dilemma - Overdoing the building of a house. I tends to plan the lots in details (by instinct not by floor plans), which make most of my lots a bit too expensive for my sims, because I usually add "unnecessary" stuff for them , it adds ups really quickly when you decorate everything. (Still, I easily forget to do it later on, so the "having clones in different versions of same house" doesn't work for me).

This might be a bit contradictory but even if I loathe the building process, having sims living in those class square- or cloned houses also take out some of the fun of playing. So I guess my own dilemmas are a bit complicated, haha.
Anyways (and sorry for the long thread). I tried to search on this forum but couldn't find any threads similar to this matter regarding budgeting (other than my own thread regarding a 5K starting funds, this one is more generic and "planning on a budget" sounds more like New Wardrobe plan to me ):

Try this trick: place the furniture of a room first. Make sure everything they need (not want) is ready. Use the cheap stuff. Get some recolors and some bedding recolors, that help. Then build the walls around that. Make sure you do the essential rooms first - bed, bath, kitchen, eating space - and keep an eye on the budget. You can get interesting shapes of houses this way, and there will be no empty spaces that you feel you need to fill. The rooms will be neither too small or too large.

I would suggest using 1 tile objects to save space, so making the house smaller plus also using a small plot of land. I have 3 10K houses uploaded to this site. They are surprisingly spacious. Bunk beds means up to 4 sim kids could sleep in the second bedroom. Now I know you like large families but something like that is handy to start out with. If you like you can look and copy my floor plans.

might do the house first on grid (paper or some program); after checking the prices.
some chance of the house being inexpensive if it has only a few high cost items.

Fortune Sims might make a house expensive if you fulfill their Wants.

Use small lots, too - 1x1 or 2x1. That way you can't make the house too big, the land costs less, and you can always expand the lot down the line with LotAdjuster if your sims get rich.

Stairs and steps are expensive, so have everything on one level without a basis. Draw your walls straight onto the ground. Economise on walls by having your sims share bedrooms, not having one bedroom each. Kitchen and dining room are one room, perhaps also sharing sitting room. The parents however will need a separate bedroom for the double bed. Do not use flat roofs, because you might have to pay for them. Sims really do not need decorated gardens - they can live perfectly well in a rectagular house in a naked plot.

With a "budget", I'm not necessary mean all sims live with very minimum funds (like maxi's 20K), but rather that the families are bit limited with what they buy to build the houses. Building for Houses for poor families are easy, but when you want to build mansions, farming lands and even castle, its very easy to drain the money up and it those families I'm struggling. (My hood is inter-grated agriculture so farming is needed in most families).

I prefer my nobles to live in separate bedrooms and want them to be on a 3x3 lot. They actually have 100-150K to build the house for, so they should have afford with the building aspects, but as I wrote in the spoilers, I tends to overdo the decorated which adds up when its about the wealthier sims and where the hood is restricted to economy classes, Lot and objects increase as high the family is in these a classes as I just can picture squeezing 4-6 sims into 2x2 or less lots who tends to have a formal parties with lots of people visiting. Going small to save money is great for the lower classes, but it wont really work that well for sims who close connected to the Politics and the Royalty.

I think Lot sizes also affect the computer specs, my computer can handle over 20 sims on a 3x3 lots, so I'm not a big fan of using tiny lots. But I do use it for my peasants who has 10-20K in funds. Most of them are cramped into less than 10x10 tile houses plus 3x3 outhouse and usually around 4-6 sims.

@ JoandSarah77.
After I started playing the hood based on a few challenges, my families are no longer "huge" and our views of Sim economy is probably very different and you probably would consider insane to believe 100K is a finance struggle for my sims, but I love using the more expensive maxi items, especially the ones from Glamour stuff packs, so its add up quickly, and fees/taxes drain it quickly. My "largest" family is a divorced woman who had 7 kids, 5 out of wedlock. The others has an average of 3-4 kids, not 6-10 as I usually gave them.

EDIT: Compare Premade Broke and Goth houses. That's similar to what I refer to economic classes.

Ah, so the real problem is that your 'hood is full of spoiled rich sims who don't know how to live within their means?

With the game, I'm not good with handling their money and even in real life, I tends to overspend on stuff I don't need (get scolded frequently for having 50 shoes. ), so in a way, yes. Nyasha. I've 20 families who has 75-150K in funds but end up being broke after finishing building their house. While the others more poor families were easier to handle as they probably need to focus on survival rather than socializing with the upper class snobs and don't need large dining and living rooms (I just put a cheap CC stereo in the garden. ).

Sometimes, I build a house I love for them, only to end up being $0 of funds when decorating the second floor, because I lack of putting a strategy on what to add, I add too much and don't have the heart to buy same objects as their servants- and can't picture a major/politician being squeezing into a tiny lot living in same bedroom as his kids.

Well, why not put a limit on how many decorations you add to each room? If it's a brand new home, it may be a bit sparsely decorated at first anyway. Besides, our simmies love to let us know what new item they want added anyway.

Alternatively, you could tie decorations into gameplay as rewards. So, in order to buy expensive decorations for the dining room, your sims have to host a successful dinner party, etc.

Or do what a lot of historical players do - force your sims to actually make the objects (or buy them off sims who have made them), instead of getting them from the catalogue. Want a fancy new painting in the hall? Pay an artist to paint something for you! (And then sneakily sell it and replace it with the painting you actually wanted)

Florentzina, I know our play styles are very different and that my idea of poor can be that a sim can barely afford the $61 rent at my hostel.

The way to build large fancy lots cheaply is to use very cheap to free cc. You can get walls and floors for 0 if you really want. Or simply decorate your hearts content and mother load them to afford it. If you want them to live in a certain style do that then bring their money back to what you think would be reasonable.

Place the furniture first - and use the most expensive stuff? And - as Jo says - motherlode, motherlode, motherlode. (After all, a hood like yours have to have rich Sims, so I don't see why they should not be rich from the beginning either).

I find a sofa can do double duty as a bed. A sink can do just fine for bathroom and kitchen purposes. The menu is going to be pretty darn limited, but Sims can even live without a stove, though I'm sure they're going to get tired of cereal and instant meals. A stove is usually one of their first purchases.

With my poor Sims, if things are really difficult, I pretend that another Sim has lent them money, and as they earn a salary or produce items, they MUST give a percentage back to the lender. I'm nice, though. No interest charges, and the lender is not a loan shark. Right now, one of my Sims has graduated from college and is working on her house. Since she will eventually start a commune or community, she wanted a large piece of land, and had to borrow a couple of thousand Simoleons from her classmate (Cassandra Goth's daughter). She just paid her off.

There are some delightful CC items out there that cost almost nothing, such as cracks and holes in the wall. A crack is not much of a window, but at least she can see out. Her house right now is a room and a bathroom, That's it. I took a house plan and basically cut it in half. While she has room to expand in time, right now, she doesn't have the funding to do so, and she'd rather not ask her friend again for more money,

As she cleans up, I deduct the cost from her income and allow only so much cleaning a day. In real life, a homeowner does not usually get paid for pulling weeds and removing dead trees. If so, I'd be rich.

Here is a thought. Not all rich and famous people own their own home. I mean even the famous house of actress Sharon Tate was rented (Charles Manson murders). They don't have to spend their fortune on the upkeep of the home.
It is possible to make a house a rental home. I built a home that was valued at $75,000 and when I changed it to rent it, the rent was $4,798 a month. Yes, they have to pay rent every month but the upkeep of the home belongs to the owner.