You enjoy working as a contractor. What you don't enjoy is doing that work and then having customers refuse — or “forget” — to pay you. After it happens a few times, you may decide that you want to start asking for money upfront. After all, getting paid in advance will help your cause because that's when people are most eager to get the job started and most likely to pay. 

You can certainly do this if you want, but be aware that homeowners often don't like to hire people who want up-front payments. They worry about the quality of the work they'll get. They may worry about you coming to do the job at all. If you have the money in the bank, they assume you lack the incentive to deliver on what you said you'd deliver in terms of quality, scheduling, etc. 

Now, you know this isn't true. You know that you stand behind all of your work, you'll do a terrific job and you'll ensure that the customer is thrilled. But they don't know that. This situation means that one of you has to do something that makes you a bit uncomfortable. Either the homeowner has to pay in advance and hope that you do the job up to their standards, or you have to do the work first and hope that you get paid. 

Your ability to make these demands often depends on the work. If work is slow, you can't be picky. If you have so much on the schedule that you can barely get it all done, you can probably ask for advance payments and simply not take the jobs where people refuse. 

Most of the time, though, contractors work first and get paid later. This can lead to uncollected debt, and then you need to know what legal steps to take to protect your business and personal interests. If you're struggling, talk to an experienced attorney.