yes, as in most States consumers have the Right to cancel some types of contracts within a three day grace period.
I would recommend not starting the job until at least the three day grace has passed and the client FULLY understands the terms and conditions of the contract. I do not think it would be a good idea or good business to ask the client to waive their Rights. If deemed necessary a post script can be added below the "acceptance" line informing the client of their Right to cancel the contract within a three day grace of the signing.( check local State Statutes to determine if service contracts fall under the three day grace.
The Contract/Proposal I posted is just a simple guide that covers most points of contention and is very easy for the client to understand.......