You need to ask yourself all of those ¨obvious¨ questions and probably more before taking the step of hiring someone that you will not be able to control very well, but, here I will outline some tips that it might help you answering those questions:
Assuming that you are new to this type of business:
1.- Always assign one simple task at the time that you also have an idea about how long it should take to complete it.
2.- Meet the person via webcam using any of the many tools offered in the internet.
3.- Always offer a fair payment (this will filter a lot of trouble for you)
4.- Keep a good communication with the person via email and instant chatting systems (not always about work)
5.- Offer respect and high values to the employee
6.- If you are having good results, say it and share it this creates bonding.
7.- Always offer opportunities to grow and share that they might be more contracts to come.
8.- A very simple one: be honest!
9.- Set a deadline for the task to be completed.
10.- Answer the questions about the task the most simple and straightforward that you can (not rude!)