Most of the marinas are around the Kemah / Seabrook area on Clear Lake. If you are actually working in Houston you'll have close to an hour drive each way in rush hour traffic. Galveston is another 30 minutes or so. Not as many marinas there though. I bought my current boat out of Watergate marina in clear lake. They seemed pretty nice around there. Had nice facilities but I didn't leave the boat there long enough to really see the whole place.
My boat draws about 6.5' and I was restricted to the channel until getting a ways out from the bridge at the mouth of the lake. After that you can sail generally anywhere in the bay. It's dirty water but in this area that's what you find. Lots of sailing around there though and I've considered moving the boat back fire a while if I ever buy a house and move back ashore.