I guess, that's not that easy, if you want to hire a person for this special problems.
In general you need to find a person you can trust, the person needs the skills and also the code quality has to be good enough.
Second, there is much conflict potential. There are many volunteers, which had worked thousands of hours in the last years for free. So why paying an external, new person instead of them?
Third, one person wont be enough, as the code has to be reviewed, bevor it can be committed. If they only hire one person, this would be very inefficient, as he/she has always to wait, until someone has the time, to review the code.