For a refractor, to cover a full frame 35mm without vignetting you will need a scope with a 2.7" (or greater) focuser & field flatterner. The smaller refractors with 2" focusers & flatteners will only cover an APS size chip generally. To cover medium format 6x7 you will be best off with a 3.5" or greater focuser (& flattener).
Petzvel refractors, like the Takahashi FSQ or Televue NP, have the field flattener built into them.
I think the cheapest refractor that will meet your requirements is the takahashi
FSQ-85ED which will give you a 60mm imaging circle, large enough for medium format photography, but at US$2995 it will blow your budget.