Scope things out well. Show up with user stories and wireframes. This will allow the developer to bid a fixed price, without getting himself in a bind later whe

Scope things out well. Show up with user stories and wireframes. This will allow the developer to bid a fixed price, without getting himself in a bind later when he was assuming a plain CRUD interface and you were assuming a whizbang AJAX UI. For what freelancers are charging, you should expect professional conduct and a solid product. BUT... not every developer knows everything. Listen for clues that the developer is getting uncomfortable and outside his skill set, as not all of them will be comfortable saying "I don't know how to do that." Money is easy - they'll give you a price. Expect to pay a portion up front. I tend to get paid every week or two when I do freelancing, always in advance of the work. And just ask if you're being reasonable. A good developer will not just blindly implement what you ask for, but will suggest easier and cheaper alternatives along the way. Be reasonable and consider the advice given by the developer. Sometimes it will be good advice. Other times, the source can be laziness, so pay attention. Also, make sure you're not working with that developer. You know, the ones who tell the snarky stories about "idea guys" and MBA's. The work they're looking for is "client", and it's their job to help them, not mock them. A successful development project requires a lot of work from both parties- so both need to carry their own weight. That means you'll do manual testing, copy writing, UI design, and provide the overall vision. That means you'll working iteratively with frequent feedback in both directions. It also means that the developer will be scrapping bits of code here and there along the way. Make sure he can handle this work style. At the same time, be careful not to abuse the agile process on a fixed cost bid. You will annoy your developer. Bottom line is that trust is the magic ingredient. So find ways to build it in both directions.