I had the same. The lady lived 25 miles away and promised to get me some customers in her estate. To her credit she did get me a few, and as a token of my gratitude I did her first clean free of charge.
That was a mistake in itself, as she seemed to expect me to clean hers for free every time! And most of the customers she got me were slow/non payers as well.
I stuck this out for over a year (yeah I know

) and was on the point of sacking off the whole area, when I picked up a couple of new customers and decided to give it a little longer.
Well my perseverance has paid off, and now I have a really good day's work there, with a second day coming along as well now. It's as regular as clockwork every 4 weeks, everyone now pays on the day and there's seldom (if ever) a 'not today'. I've sacked off all the slow/non payers. Some of them have even approached me recently (thinking I've forgotten/forgiven their debts)!
Life is good!
John