Steve Foley wrote:
So if I bought a damaged aircraft for $5000, repaired it, painted it, and
sold it for $50,000, I would be liable for taxes $45,000?

No, because you would have spent money on parts to repair it. That
money spent would be added to the $5000 for your basis. And since this
is aviation, no doubt that amount would now be MORE than $50,000. :-)