Hate to say it but buyer beware. Also never sell a car to family or friend because they DO go wrong especially something as badly made as our favourite cars were.
As a rule of the thumb in their day a mk1 or2 mini would be an oil leaking rust bucket long before its tenth birthday, sure there were exceptions but when buying put away the rose tinted specs and use your head. Minis were always of a dodgy design and build quality designed to be put together by unskilled labour with hand held spot welders and a panel fit of where it touches. I do love minis but do not ignore the reality of the poor design (from a durability point of view) and build quality