I had a 70 VW Bus painted a 1968 Pontiac blue. She had the 1600cc engine which around town, to the mall, back and forth to Baltimore was great. A trip to Altoona,PA convinced me to get Porsche engine. That one had twin carbs. As with any car, doing your own maintenance will save a buck and keep you knowledgeable about little things that are in need of maintenance. Chilton, Haynes and the best one IMO is How To Keep Your Volkswagon Alive. Its got pics, very few "better save this repair for the garage." This manual also, gives you the how to to make necessary tools to repair VW's.
I didnt have a problem with rust and I owned that Bus from 83 to 97. I covered the flat area, driver side to passenger side and from behind the front wheel well to in front of the rear wheel wells with sheet metal. Your heater tube is under there and the shift cable. Nowadays, you can undrcoat yourself and that is a great way to the body life.
Parts, join a VW club, definitely.
Rather then rely on air to cool the engine. Invest in the aftermarket oil cooler, this will extend engine life should you have a 1600 cc engine. Consider too, helicoils for all the head mounting studs. The aluminum magnesium engines after many miles will allow the studs to loosen to the point the threaded stud hole is too big(stripped) to keep the stud tight, so you loose compression.
Depending on your climate. The VW thing had a blower in it you can mount in the driver side rear of the Bus engine compartment giving you quite comfortable heat. Its true the Bus is stupid easy to fix all around. Oh yeah, consider insulating behind the interior removable panels