Post Housing will be kinda hard to get at Ft Sam as a student, but you can start looking at apartments online. Most nearby aren't the best.
It's only 6 months though, so just have the fam roll with the punches.
20 weeks or longer is a PCS move.
What you CAN AND SHOULD DO on your end is ensure you take MAXIMUM leave to set up things in TX VERY close to post (What this means with FULL CAPS LOCK ON is to have YOUR HOUSING WITHIN 5 MINUTES FROM POST INCLUSIVE OF TRAFFIC, otherwise you will end up like my dumb ass and have a 45-1hr commute in the evening when you should be studying or spending time with fam). If you blow that one off you will regret it, just for gas bills alone....so live close . So take 44 days leave and ensure you take permissive TDY on your loosing installations side (a total of 54 days) as your gaining side will most likely not let you take permissive TDY. You can also sign in to your new unit early, so take 44 days and if you need em fine, if not sign back in.
Its a really good school you are going to, and I am happy for you, but don't blow it by living too far away. Even 6 miles away in San Antonio evening traffic will SUCK.