I don't like to ask for a deposit because I think it makes the customer feel more secure if they are dealing with someone who has the resources to pay for the materials. Working capital in accountant speak. I know plenty of slackers who need the deposit money to pay off the supplier from the last job so that they can re-open their line of credit. The keys to the customers house are security enough for me.
I understand some of you have been burnt or cancelled at short notice and therefore a deposit is essential. I don't mind being cancelled as I can always go and tie up all the loose ends I have left elsewhere
The only payment disputes I have had have been where people have been unable to afford to have the job, usually replastering, done properly so I have patched up and they have been unhappy with the result. I have learnt, to my cost, that if a customer can't afford to do the job properly, then it could all end in tears so I walk away.
I build in profit to all my jobs on top of the materials and day rate which I use as a cushion to cover things like replacing fixtures and fittings and the extra cost of paint for feature walls for example. I then use this cushion to deliver the little extras with a smile on my face and leave a happy customer. If someone starts getting difficult, I can then point out all these little extras and they tend to realise that they are being treated well and are happier. If they don't, then I withdraw my goodwill and if necessary finish up the room I am on and don't return. I did that twice last year (once to a teacher an once to a banker!..see teachers thread...)