http://www.unlimitedsims.com/index.php
The preview is a full chapter about the use of apartments. Really
interesting to read.
For instance if you build apartments yourself make sure to fully furnish
them. If a playable Sim moves in most of the furnishing will disappear
(there's a list of stuff that stays), but if a Townie moves in he can
live there without missing anything.
There are also some good tips about noise and problems surrounding it.
*Bianca