SOMA is the expensive part of SF, rent wise.

Your other option is to live close to 24th st BART station. It's not close to SOMA but it takes 10-15 minutes to get to Powell or Montgomery stations and another 5-20 minutes walking to any place in SOMA (depending where it is exactly). BART runs very frequently (every 15min on weekdays) so you don't wait more than a few minutes on average.

I did such commute for a few months (from 16th/mission BART stop to an office close to 4th/king st in SOMA) and it was about 35mins.

I suggest 24th st rather than 16st as I assume that part of the town is cheaper but you can look anywhere along BART (personally I live close to 16th/mission and fully recommend that neighborhood).

It's going to be difficult to find many places that have four bedrooms in that area much less affordable. Most in that area are two bedrooms with some three bedrooms. If you guys don't mind doing like a two two-bedrooms, the Avalon isn't too bad. They got like three buildings and all are in a row, across the street from the Caltrain for easy access to the Valley.

I'm looking for a 2BR

With the difference in rent for live/work places in say the Mission and other more central neighborhoods, you could all get bikes for easy access to Caltrain and still have a lot left over.

Disclaimer: I live in SOMA.

Ah ok. Thanks. Any good communities you recommend in Mission?

Mission is rather small, I'm not sure it can be subdivided further into communities.

In general I recommend the block delimited by castro st. on the west, valencia st. on the east, market st. on the north and 24th st on the south. The parts west of mission st. and north of 24th are more sketchy.

I would suggest investing in a few day stay in SF to check out various parts - after all what is sketchy to me might be colorful to you (or vice versa) i.e. you can't assume that your taste will match the taste of people giving recommendations here.