Auto repair tip:how to get ripped off

This is a tip about how you get ripped off when you try and help somebody else out. So I answer an ad on Craigslist for someone needing an exhaust manifold leak repaired. 3 days after I reply to the ad the owner of the ad respond back asking if I can still do the work. And meet up with him the following day he tells me he has the parts explains that he already had somebody else try to repair the leak. Previous repairman had the vehicle for 3 days didn't repair the leak. The following day he drops the vehicle off with new manifold new gaskets and new bolts, explain the previous repair man broke off two studs in the head attempted to drill them out and replaced with two bigger bolts. I have my nephew attempt to help me with the vehicle removing the stock exhaust manifold, we work on the vehicle until 4 a.m. the first night. The whole time I'm keeping the customer updated throughout the night with texts and phone calls explaining all of our progress. Also the first night that we worked on the vehicle discovered that he ordered the wrong manifold once we got it installed obviously our mistake for not comparing before we tried to install it but as it is it was the wrong manifold so we reinstall the stock manifold with new gaskets bolt everything back up 7 p.m. rolls around that evening the guy that pops up out of nowhere as we're starting the vehicle he hears that it still leaking, we stand around discussing what the issues were with the vehicle not getting repaired. Customer then goes on to nonchalantly explained that he is not going to pay the $250 that we agreed upon or any amount for that matter for the labor that we put in on the vehicle to try and fix what somebody else had already broke. I did fail to mention that the first day he dropped the vehicle off I had asked for deposit and this should have been a key that the guy was going to try and burn us because he was very hesitant to even leave and $80 deposit he did however leave a $40 deposit to get the work started so all in all between myself and my nephew we only made $40 for all the work and labor that we put into this guy's vehicle which in the end I think he already knew the exhaust manifold wasn't the issue I think he knew it was a bigger problem than what he stated. We did discuss with him before he left without paying is that the problem most likely was the previous repairman that he had work on the vehicle most likely drilled through the aluminum head into one of the other exhaust ports on the head or there's just something majorly wrong with that head. Thanks for reading moral of the story is always trying to least get a 50% deposit before you start any work on Strangers car.