When you start doing business with somebody you don't know there is always somebody the wrong side of the money.
This is why they have sites like scriptlance or rentacoder etc...so you can find people for these jobs and not have to pay them upfront, or have them trust YOU are not a scammer.
You pay the site, the designer knows you are good for the money, and that if they do the job they will be paid, they do the job to your satisfaction, they get paid etc.
Of course, no guarantee that you will always find people who will get it right first time, but in my experience they will keep going till they do because they know money is waiting for them. They also fear the dreaded bad feedback.
A lot less drama that's for sure
