'The prison contracts everything from security to mopping.'

In the vast majority of American prisons, the prisoners do the mopping. Security is still done by guards, but nearly every other job in the prison is done by the offenders. It's much cheaper this way - for state prisons average starting wage for non-industrial jobs is $0.25/hr. Industrial jobs don't start much higher, but they tend to have a higher cap around $2.50/hr instead of the standard cap of $1.00/hr. There are a few cases of offenders making minimum wage, but these are the exception rather than the norm.

Prisons are run by the offenders - it's cheaper this way.