Honestly there's profoundly little you need to know to get into the MVS, the most important asset you have is your location.
In Texas you should be able to find a Candy Cab or a regular Full Size Cab locally, I've seen them on this board alone a lot so I'm sure if you check your phonebook you'll find some distributors or even check eBay.
The reason location is important is because the shipping on a cab is murder, it almost always has to go frieght and starts at about $100 all the way up to $300, just to move it from point A to point B.
Aside from that, what you should look for in a cab... the bigger the screen the better, nothing under 19" if you can help it, something in the 20's is optimal for a stand-up cab, you might be able to get one in the 30's for a candy.
Now if you decide to go the full size, make sure you'll have the room. I, for example, have a game room to keep it in and a nice garage to work on it (minor touch ups).
Make sure the screen has no burn in and is in good working order, that's perhaps the highest priority next to the structural intergrity of the cab itself (if it's rotting, it's no good). A new monitor costs about as much as another cab would and you could kill yourself installing it.
If you can find one with an MVS mobo in it already, good on ya, if not, make sure it's Jamma+ compatible.