Regardless of what your budget is the most important thing when buying a FJ40 is that it be COMPLETE and mostly RUST FREE. If all of the parts are there and the Tub is OK than if is easy to make a good driver but Tub issues are much harder to deal with and more expensive.
As far as paint goes, that is one of those jobs that you can spend as much as you want. However we usualy spend between 4-6K to get a 40 painted (better than new).
I have a customer that is about to put his 79ish FJ40 up for sale and it will be in the 10K range depending. It is white w/ a hardtop and also has a small lift and ~33" tires. Please feel free to contact me with any questions.