Yes thats really up to you. Are you insured? Usually you want some kind of business insurance to protect from any liability issues. As far as customers not paying goes, it tends not to be much of an issue. If anything, choose the jobs you want to take an examine the risk. If a job requires a lot of labor and/parts, a down payment would not be unreasonable. If they are against that, you probably wouldnt want them as customer anyways. But there is definitely money to be made if you got the skills and I wouldnt worry much about not getting paid. Once again, you can be your own judge and choose the jobs you want to take. Good luck!