Legal Question in Construction Law in California

Well yes and no. Many people hear about the $1,000 or 10% whichever is less rule, but that only applies to home improvement contracts, swimming pools and certain other "consumer" contracts. It is, however, illegal for a contractor to bill for work not done or materials not ordered and committed to the job, or a "reasonable" deposit. So to be strictly legal, the contract should be signed, the materials ordered and then you pay for them, and the total amount should not exceed the cost of materials plus a "reasonable" deposit. Realistically, if the contractor has a firm bid or price for the materials and the amount he wants on signing is appropriate based on the materials cost, it would be considered legally acceptable.