This person must know the tool "balsamiq mockups" well + have attention to detail.
He will be given a screenshot, and will have to create a "balsamiq mockups" prototype from it.
He has to do ZERO creative functions, his job is JUST to copy the interface from the screenshot to the "balsamiq mockups" format. It requires very little skill, but attention to detail has to be very high. Most people can cut corners. A lot of them are lazy. I need attention to details.
I want to find someone who will do this work cheap and will value the job. People that have skills and can do prototyping in balsamiq mockups - will probably find this job boring, as long as it is just copying (with high requirements to attention to detail). So, ideal candidate will have beginner level skills in prototyping - but will be willing to learn and work hard.