Are there laws to limit the amount of a deposit you can receive from a customer? On a contract job what percentage is a fair amount for a deposit? I do 50% to start and 25% at rough and the 25% left at final. I have thought this to be fair and it gives me something if a customer decides not to pay.
In electrical work there is usually a lot more work to rough than final. I usually estimate the final and make that the final payment. Depending on the size of the job I may have an advance and rough payment also. On the smaller jobs with an established client I might only have payment on completion.
Basically, the longer the business relationship, the less I ask for in advance. There are no rules that I'm aware of. The contract is an agreement which includes the method of payment.
What is more important then a deposit with the contract, would be your progress schedule of payments, another point to remember is what will the amount of purchased material be, consider a job that has special ordered items, these items may require advance payment, in this situation, the contract wording, may allow a larger down payment.
Contract law, is a field of it's own, and every state has different views on contracts, best to get good legal advice up front, it may help prevent problems, that can lead to considerable losses.