Wow, the breadth and depth of the Internet never fails to amaze me and I think it's still in its infancy!
Good questions and I certainly don't have all the answers but I can pass on a couple of thoughts.
Assuming that you can purchase a vehicle in the States and use it (and I don't see why not) you really need to find a bus that has already been re-registered (and titled) for private use; either as a truck, private bus, motorhome, etc (terminology and available categories will change by State). Just make sure it is not
still registered as a commercial vehicle (or school bus); otherwise you may be subject to getting a CDL (Commercial Driver's License) which would not really be a viable option. I have no idea how you would handle the insurance situation.
If you can find a bus whose seats have already been removed you'll be ahead of the game! Most of us think that seat removal may have been the worst part of the conversion!
If you can fly into Florida I'd certianly suggest you talk to Greg Archambault; he's a wealth of knowledge and a real staight-shooter and has a website here: http://flbus.tripod.com/
. I think he's pretty much a one-man operation but he's always got a bunch of buses that he either has or knows about. I've never heard anyone say a bad word about dealing with Greg (and NO!...I'm not realated or on the payroll!
I think within two weeks with 2 or 3 folks working you could get a decent conversion done. Make sure you're near a Home Depot (that's a DIY home improvement center and also happens to be the largest retailer in the world) and a Walmart (everything that Home Depot doesn't have
) and you'll have access to darn near everything you need. I did a quick conversion in my bus for a trip in October; I grabbed a bunch of 2x2's (a standard lumber size; say about 50mm by 50mm), a bunch of deck (drywall) screws, and borrowed a wide crown pneumatic stapler (could also be rented) and went to work. Ended up with an enclosed space for a portable toilet, counter with a sink and running water, a couple of built in bunks, a couch, and a couple of really comfortable seats (these came from an early '90s Chevrolet Astro van for $100 for the pair in beautiful condition; I went with van seats since they're normally mounted on flat floors).
You could run a small college dorm/recreation room sized refrigertor off an inverter of 300 to 500 watts or so; that size is small with built-in outlets and requires a simple two wire connection to the battery (or batteries). Or you could use one of the 12-volt "coolers"; they're only good for about 40-degrees below ambient temperature though so you'd have to be careful in hot weather. There are some portable 12-volt refrigerators but they're pretty expensive if you're going to turn right around and unload stuff when you head home.
I'm sure I'll think of more but this should get the ball rolling and hopefully a bunch of other folks will chime in here too.
Good luck and welcome!
 And another thought might be to check out eBay (http://www.ebay.com
) and see if you can't score a bus that not only been re-registered/re-titled but also made into a camper (not necessarily a luxury motorhome). Also check Truck Trader online (http://www.trucktraderonline.com/
), Equipment Trader online (http://www.equipmenttraderonline.com/
) and RV Trader online (http://www.rvtraderonline.com/