Is it permissible for the homeowner to cancel his agreement with the first craftsman and contract with another, better craftsman, and is the first agreement considered a binding contract that cannot be rescinded?

An ijarah (lease/hire) that is delayed in its commencement requires an upfront payment of the wage to the worker. This is because delaying the wage along with delaying the start of the work leads to the prolongation of both obligations (ta'meer al-dhimmatayn) and the invalidation of the contract. Thus, the contract that was concluded between the two parties is considered invalid and dissolved. Consequently, your companion is permitted to cancel the first agreement and enter into a new contract.