That's the main problem with modified vehicles-- they simply become maintenance nightmares and a constant money pit. The owner finally has had enough aggravation and puts the can-o-worms up for sale.
The flipside is the new owner's excitement of his purchase quickly turns into anger and disappointment because he got suckered into buying someone else's problems.
Thus, given a choice-- I would always prefer a 100% OEM Stock vehicle over a modified vehicle.