There are a couple of web sites that deal extensively with Mamiya TLRs. I don't remeber the urls but one of them listed things to look at when buying a used mamiya. One thing to keep in mide is that Mamiyas where the cameras of choice for many years for portraits and weddings, so many of the used cameras have seen heavy use. Of course one of the reasons they were used so much was there amazing durability.
An advantage with the Mamiyas is that if you need work done, almost any camera repair shop will have experience and parts on hand. Also if you do accumulate a set of lenses it is not a huge outlay to have to buy another body if the original breaks and repairs are more then a replacement camera.
I have used the 220 and they are great cameras for the kind of use you plan. And as others have pointed out, there is a huge amount of accessories out there for both 220 and 330s.