I've owned a number of VW's over the years, but have paired it down to 3 at the moment; a 66 sedan, a 70 vert and a 78 bus. VW's can be very reliable, but do require regular maintenance. As you have heard from the various stories, people tend to drive them until they break and then complain about reliability.
A 74 should be a 1700 cc carbed engine. If you buy the bus, equip it with a cylinder head temperature gauge. The biggest issue with this engine was cylinder head temps over 450 degrees causing the valve seats to drop out of the head. A good digital cht gauge will prevent the problem. Remember this engine was designed in the mid 30's and like all engines of the era they had a short life (compared to today's equipment).
VW buses have the aerodynamics of a brick. You'll fight every side wind just to keep it on the road. The gas mileage will suck. You'll probably get 15 to 16 mpg. But... Little kids will be awed and even the most anti-social teenagers will flash you a peace sign. The bus is just plain fun to drive.
You can still find rust free buses in good condition for $4000 to $6000 here in California. If you want a fully restored bus expect to pay $10,000 on up.
Oh and remember it's a bus not a van!