I must agree with flyingfemme - unless the seller is a complete mug this cannot be worth doing.
There are so many issues with buying a used plane especially one of that age - in aviation there is no systematic way to locate all records of the maintenance history (unless all maintenance over all those years has been done by the same firm - most unlikely) and this is going to verge on the impossible with something imported.
I know a few people who have bought sub-20k planes and they've all had 5k-10k annuals since, and that's on a UK-purchased plane. You buy cheap and then spend the money on maintenance - unless you get lucky (which some do) there is no way around this.