I've read a few projects lately with buyers saying they've been burned by freelancers, and have had to repost projects because of bad service. It doesn't have to be this way.
Save yourself time and money by realizing no one is going to give their 100 percent best for a low paying assignment. If you offer someone a job requiring $500 worth of work, but you only want to pay $100, then you're going to get $100 worth of work. It's all too easy to accept a low paying job, take the money, and then do a quick, crappy job or no job at all. But usually, when people are paid professional rates, they provide professional work worth your money. Also, always view a freelancer's portfolio before hiring them so you can judge the quality of their work.