1. If he is the executor can't he sell both the house to you and the land without going through the foreclosure process?
2. If you enter into a contract to buy the land for $15k but wait until after the foreclosure sale to close, couldn't you purchase the land from the son "subject to" your winning the bid at the auction? In other words, if someone out bids you at the foreclosure sale then you would not be obligated to buy the land. But if you do win the bid at the foreclosure auction, then the son would be obligated to sell the land at the predetermined price of $15k.
3. Is the 1st upside down or just past due? Would it make sense enter into an agreement with the son that allows you to buy his land and to take legal equitable title to the fathers house, bring the loan current, then fix and flip the house and land....paying the son his $7 to $15k after you completed and closed on the flip. The son's $7k-$15k is coming from the end buyer at the final closing of course.