The answer is both "no" and "yes." "No" in that the law does not require a waiting period--in theory, a sale could be done & closed on the spot. "Yes" in that many of the things that have to be done--checking title; getting title insurance and any other insurance required by a lender; an appraisal if  necessary for a mortgage and getting mortgage approval; inspections, if there is an inspection clause or contingency in the contract; etc.--take time and will add several weeks, or possibly even a few months, to the process.