I have two tips for finding an apartment in SOMA:
1. If you want to save money on rent, go to the southwest of the neighborhood. The closer you get to South Park and the Bay, the higher the rents go. Also, the cool thing about SOMA are the lofts and most of those are tucked away on top of buildings on the southwest side.
2. Make sure you get a parking space. Parking around here is impossible and if you leave your car unattended out on the street you will have to replace windows (and maybe worse) every six months or so. This area gets pretty desserted at night and is a prime locale for car break-ins.