We bought our 87 f250, gas 460 when it was 9 years old and it had around 100,000 miles on it and it had a fifth wheel hitch in the back. it was in very good shape and we used it for hauling alot of very heavy loads , Over 20,000 lbs with a goose neck and over 12,000 with the bumper pull. and we didn't replace it until 2002, when we bought our 2000 f350. We still use that 87 for short distance hauling, under 50 miles ,
The 2000 we bought it with 78,000 miles on it but it was in excellent shape at 2 years old.
Those 2 trucks were trouble free and very good buys.
Now we broke the trend and bought a new truck because It's probably my last truck and I wanted the 6.7 with that new exhaust brake .
But one key that has worked for us is we have always bought the best truck we could afford with out any payments.