I have had a few quotes from window fitters from this site. I chose one tradesman I was happy with and offered the job. (Supply and fit 2 double glazed so windows) I am happy with the price quoted and was expecting to pay the bill upon completion of the job. However after discussion the fitter had stated he needs a 'deposit' before buying the windows on my behalf and that this is common practice. I'm wary of paying money out to anyone before the job has been completed satisfactorly. Is it safe to pay before hand or should I avoid? Thanks