use sites like Elance and others or post on hacker news as it's read everywhere. Contracts are okay but they mean shit if things fall apart. There is no way you are going to sue anyone in Eastern Europe. Do a good job interviewing people and check whatever references, github resources and anything they have.
Once you find the person(s). Make sure you pay a FAIR wage as everyone has bills, family and extended family to look after. If you don't they will take on other jobs and juggle tasks. Have a contract (see above) that spells out tasks, payments tied to deliverables and deliverables must include all source and any third party libraries. This includes Photoshop psd files or whatever. Validate what you get and it builds. Pay a token amount at the start if you are comfortable with the person/team. Also look at providing bonuses at the project close. One other thing: never go with the cheapest person.
Provide very detailed specification, drawing, wire frames, etc... no matter how minor you think it is. Never, ever, ever assume it's common sense. You would be surprised how some people around the world think or interpret things. Make sure the team is on Skype, or other tool, and be available to them when they need you or anyone else.
Read up on Zapier as they started and still are a distributed company. https://zapier.com/about/ Have a look at their company blog as they discuss remote teams. https://zapier.com/blog/
Remote teams work but you need to put a lot of work into project management and keep on top of things. So if you don't have time for this and detailed specification... don't go down this path.
