@Vincent Plant
This seems to be an underlying problem with contractors. I'm up north in PA and the same things go on. Most of the time though we don't even get to the deposit stage, because they fail to show.
I am an extremely aggressive person when you don't want to work. My first step here would be to start the ball rolling on breach of contract, whether you use an attorney or file at small claims yourself is dependent upon you. If you choose not to start the claim then at least become aware of the process.
There are two ways to gain education. Traditional schooling and our school. The school of hard knocks. I will suggest somethings. How do I know these things, well let's just say I too have attended the school of hard knocks.
On signing the contract I need a copy of your license, bond, and proof of insurance. I also need a record of 5 roofs completed in the last 6 months. I don't always but I may visit some of those house's and say "I passed by a few months ago and saw a roofing crew here. Did you like them?, I'm having my roof done and need to hire a great company"
I got this, awhile ago, out of J. Scotts' book on flipping.
10% on contract signing
20% after the first days work is complete
30% after half the work is complete
30% after substantial completion of project
10% 2 weeks after completion
Pricing is negotiable not hard and fast. The biggest thing is to keep them hungry. Once they have the cash they have no incentive.
On another note any contractor that says I need money up front for the supplies is running a day to day operation not a business. With that being said if I really "like" the guy and he is insistent on needing money for the supplies I tell him put a list together and I will pay direct to the supply house with direct delivery to the jobsite. A bit more work on my end but at lease when he doesn't show up I have the supply's and now I'm just looking for the labor. I'm not out that cost.
Just know that we have all been there at one time or another. Don't let it shake you out. Push through and take good notes on "If I knew then, what I know now" so on the next one you are a few steps ahead.