One advantage of a prebuilt kit car is that they usually come with some kind of warranty on the build and parts to a degree.
If your home built one has a wheel fly off at speed, it's all on you and your deductible.
Often as well, if your friend has found himself over his head, a good portion of that is going to be tools that he needs to buy. Things that normal people don't have like torque wrenches and brake calliper pliers et cetera can add up quickly.
Before I do anything I ask myself “Would an idiot do that?” And if the answer is yes, I do not do that thing. - Dwight Schrute