I'm hoping my experience will help some of you avoid it! A guy named "Bob" (never got his last name, but he lives on or with a family on Buenos Aires near the school) left a flyer on my door last spring to do miscellaneous worker like gutter cleaning, yardwork, etc. I hired him to clean the gutters as I'm afraid of heights, and he did a good job, and came back and did it several other times. I always paid cash (huge mistake!!), and one time he offered to fix shingles on the roof-since he had to buy the shingles, I gave him the money upfront (he'd not let me down before), and told me it would be done the following day while I was at work. He came back and cleaned the gutters once more and offered to put up gutter shields. Again, I gave him the money since he had to first buy the shields ($130), and never saw him again. This was on 11/14-I called him after about 10 days and he said he had the flu and assured me it would be done the next week. I called again about 2 weeks later and whoever answered the phone basically told me it was "stupid" for me to have given him cash and they didn't know where he was. (Well, she was right, but I'd rather think I was too trusting).
I had my son check the roof, and he also never did replace the bad shingles. So I'm out $200. If you have anyone come to the door and offer to do repairs, learn from me-first of all, if they get hurt you could be sued, second-don't pay upfront. A guy who looked suspiciously like "Bob" was around this past weekend offering to trim trees...