There really is not an affordable medium format digital system.
Once you get lenses and other things you will be spending some serious cash compared to A Canon or Nikon digital system and honestly unless you are a making 10K on your day rate like the above poster says you don't need it.
Now if you just want to shoot film, a medium format film scanner can be had cheap and medium format film gear is not expensive in the used space at all.
you will learn far more about being a good technical photographer shoot 100 manual focus, manual exposure slides, than filling a digital card with 10x those images.
If you want to learn digital, get a camera from Canon or Nikon, those you can buy without a home equity loan. If you must spend 20k you can get into medium format digital, but for that you can solve the problem in different ways.