Many contractors rightfully request cash deposits from customers prior to starting large projects. However, this is when much contractor fraud occurs.
Never pre-pay a contractor in full! And, never hand over a deposit without first obtaining either a receipt and/or detailed contract. Obtain personal information, most importantly the contractor's full name, home address or other personal or business information. Trying to prosecute a 'bad contractor' or get your deposit back can be very difficult if you can't prove what was done or who did it.