For quite some time my company is super busy with our apps, and a few days ago someone contacted me by email offering his services to help me as a graphic designer. He has a fair price, a flickr portfolio (with great stuff but not popular at all), same on Twitter. I was really considering in hiring him for some specific service, but the question is... what precaution should I take when hiring someone I have no idea who is? I can't even be sure I have his real name and his real country. How do I make a contract? How do I pay? How do I know he will not sue us after the graphics reach the App Store asking for more money? And of course, how do I know he will actually do the service and not steal from some stock service? Am I a bit paranoiac or is this a common deal with graphics designers? PS: if someone asks I can provide his flickr, but I think this is a general question and not specific for this designer.