I'd recommend old Fuji.
For around or less than $800, try the used Fuji fixed lens 690. You can have both the 65mm lens version and the 90mm lens version.
The 90mm is sort of the standard lens,like the 50mm in 35format, while the 65mm is about the 35mm in 35 format. You get 6x9 film size.
This is no WLF, not a SLR, but like a big Leica M. The biggest problem is, if I may say so, it's not digital capable.
A better, my opinion, but more expensive choice is Fuji GX680. It's WLF SLR. 6x8 film size, a lot of movements (tilt, shift), this is the largest medium format, or the smallest large format.
You also has the choice to use digital back. You can even get a stitch back adapter that gives you effectively 4x larger sensor area. No other medium format camera can do this yet.
About a year ago, GX680 had been sold on ebay and luminous-landscape for more or less $2000, complete system(full outfit, 3~4 lenses, etc.etc.).
The above would be the absolute cheapest.