Good choice of sensor as it is a larger sensor despite being "only" 39MP. The larger the sensor the more of the MF look you get
especially considering that 645 is the smaller end of medium format.
36.7 x 49.0 mm vs 33 x 44 mm makes a difference. Better viewing, shallower depth of field and more optical resolution captured.
Good price on a complete camera. If you either upgrade or decide that MFD
is not for you you should be able to sell it at a similar price. Buying new MF gear would
result in quite a loss. Entry level MF gear loses a lot of value on the used market.
Phase One IQ140 sold for $12,000 just over a year old on ebay while it costs $21,990 and is a latest generation back.
The Camera you are getting will pretty much take the same picture as a $25,990 IQ 140 kit.
Being that you are buying used proceed with some caution. If it's ebay check for good feedback and return policy.
You could also consider sending it in to Hasselblad for a checkup and tuning. They have fast turnaround.
Have the camera sent to you. If it looks nice send it off to Hasselblad for a checkup. You should be able to do this in the 15 day return policy
window. Give Hasselblad a call before going ahead and check how quickly they can take a look at it for you.
You could also have the seller send it to Hasselblad directly, but you would have to commit to the price of a checkup
without seeing the camera first.
Instead of saving up for a more expensive Phase a year from now use that money to add lenses when you have the money and start shooting MFD now.
More lenses will make a much bigger impact on your images than a few more megapixels and a different LCD screen.
You could also use the saved money to add an 8x10 film camera...