Who says he’s a contractor? You or he? He doesn’t sound like a contractor. Depending on the situation, there is nothing wrong with paying a tradesman or handyman by the hour, but you should ask for an estimate of time to complete upfront. As a general rule, you might pay for a small project by the hour; larger projects should be agreed by cost. Always be sure if the cost includes the materials. Be flexible too, remember that many projects have hidden issues which will not be known until work starts. But make sure s/he knows you don’t want to hear about any surprises at the end. Make sure you tell the person to speak with you about them as they appear and not when you are making the final payment.