Ok how do i get a playable ghosts?I've heard tons of things and i don't know what is true.

Here's something from the Prima Guide on Sunset Valley...
If a loved one dies and you have their marker, there is a chance you will get a call from the Landgraab Industries Science Facility. The scientists have found a way to reverse death! Choose the Restore Ghost option at the Science Facility to bring your loved one back from the dead. Sort of. It turns out technology isn't perfect. Your loved one is returned to you as a playable ghost. They appear as a selectable Sim, with all of the regular interactions and socials. They can develop skills, cook, and attempt to live a regular life.
I haven't tried it yet myself so I hope it works for you : )