The last MPI which came into my family was a 1997. It had an MoT (oh, yeah) and 'a few small bubbles.
However after looking at it in detail before buying we identified a lot of in-depth corrosion and what might have looked like a simple job turned into a huge resto job.
It needed new windscreen scuttle and to of bulkhead replacement (just a few small bubbles!), new inner and outer sills, new A-panels, front subframe to floor repair both sides, new door skin on one door, rear quarter panel repairs plus inside rear side box, rear of boot area and bumper flange plus rear scuttle panel, one new front wing, plus a few more bits and pieces.
This was my Grandson's car and we did all the work between us, only paying for a re-paint which was done at 'mates rates' by a friend.
I reckon had we had to pay for the work to be done, it would have cost more than the eventual value of the car. It cost us just the price of the new panels.
If you buy a Mini, you do need to be either rich or have the skills to DIY.