Fastest way to get this is adoption, cakes, money, and murder. Just adopt a child, force age to young adult with a cake, have them adoptand repeat until house is full. Drown the 7 older sims in a pool and repeat.
Adoption is 1000 bucks a child so if you run out of money I have a trick for about 20000 easy. Hire a nanny, befriend nanny and ask to move in. When they do you get their funds which is between 18-20k.
Hope this helps!
**Update** Multiple sources have stated that instead of murder you can just manage household to remove Sims. Murder works great if you are working towards any ghost related cheevos as well.