Iknow this is a late posting, but the topic realy gets to me.
Absolutely NOT! Do not pay anyone that much up front. After what I've been through, 50% up front is scary. If it is a well known and established company with a good BBB record and references, I will pay 50% up front. But if it is a small contractor, I only pay 25% up front, another 25% when halfway through, another 25% when finished, and the final 25% after I'm thoroughly satisified.