Tanguy-actually, since you know where the customer lives and what they drive, they will pay you....especially in my case since in all likelyhood, I have already taken pictures of their freshly detailed car-in front of their house.
I have only had two problems. One was a hot check that I was unable to collect on. The woman was evicted from her house a week or two after I did the work and I was unable to track her down. I turned over the check to the state, but I guess they've never found her. The statute of limitations has run out by now anyway.
The other time was a 1992 Bonneville. It was a little out of my normal area but it had been a slow week so I took the job. The owner was selling it and wanted it cleaned up. He said it was in excellent condition and it shouldn't need much (which always scares the you-know-what out of me) and his wife would be at the house. I get to their house and only the kids are there. The car, as I expected was a real POS. Ground in grime in the carpeting, scratches, scuffs and spider swirls in the paint, etc. I put about 4.5-5 hours into that car and I was pleasantly suprised that it cleaned up well. By then, the wife had returned home, looked over the car and seemed really pleased.
About 8pm that evening, I get a call on my cell phone. I recognized it as their number and the voice as that of the husband. He says he got my number was a friend and asked when I do a detail if cleaning the engine was included. I told him I didn't do engines without a signed release because of the the liability I could incur if any electrical parts were damaged by washing. He then asked if I guaranteed I can remove all stains and scratches. I told him I didn't and that no one could guarantee that. Some stains are permanent and deep scratches require repainting. I knew where he was going, there was a small red stain that wouldn't lift at all, a couple of scrapes that were into the primer and I didn't do his engine because he when he originally called and asked what a detail involved, I didn't mention the engine and without someone of legal age at the house to sign a release, I wasn't going to anyway.
He finally told me who he was and that he was disappointed in the work. He then said he was sending his wife out to me to pick up the check since he was mad at her for paying me. He said when I came out and removed the stain, scratches and cleaned his engine, he'd give me the check back. He ended up making his wife drive 30 miles (one way) to me to get the check. She was thoroughly P.O.ed...at him, not me. She said she told him that red stains can be permanent, they even had one in their dining room that wouldn't come out and she also agreed that fender needed repainting. I told her there was no way I was coming back out to their house and put another second into that car for her husband. I wasn't going to drive all the way out there again, spend another hour or two and have him find something else to nitpick and not pay me. She said she understood and would tell him.
He called me up the next day, all mad at me about not coming back out. I told him I didn't trust him to pay me and he can find someone else to put up with his crap. I then hung up on him. He called back and I hung up on him again. I guess he got the message because he didn't call back after that.
Since then, I have insisted an adult be at the house (with new customers) to go over the vehicle with me before I start. If no adult can be there, then I reschedule.