I would second David's advice of going with the Hassy or Mamiya RZ/RB. The only medium format lenses that my local camera store rents are for the Hasselblad system. (CF/CFi lenses) If I wanted to drive the 1 hour or so into San Francisco I could probably rent other brands also, but usually I don't want to.
For $2000 you could get a very good condition used body and a great lens from KEH.