The last month’s rent deposit should be dated for the present date as you are supposed to have that deposit before the tenant takes occupancy. If you do collect a last month’s rent deposit you do have to pay interest on the deposit annually. The first month’s rent could be postdated for the day the tenant is moving in, however there is a risk that the cheque could bounce and you would not know it until after the tenant is already in there, the best practice is to ask for cash or certified cheque for the first month’s rent.