Slow payers go with the job I have found,
I have not collected for years, its tough to start with but once your arrears find there natural level your cash flow settles down and you get used to it. mine runs at around 6k
I have some bright yellow stickers which my lads attach to the "just cleaned" slip for anyone who owes more than 3 cleans.
it says, Friendly Reminder... Whilst friendship is essential to the success of our business, financial support is an absolute necessity. May we enjoy both?
Its usually enough to prompt them and payment follows quickly. If not I send letters but only need to do it 2 or 3 times a year.
I refuse to collect, I have found if you do it once they seem to expect it. "It dont matter if I forget to pay, he will come and get it if he wants it!"