>The best skill you can have in most prisons is plumbing/home renovation knowledge, as it's common for one of the guards or warden to have you fix their houses in exchange for a restaurant meal on the way back to the prison. If you work well you will be contracted out F/T to the local town and the guards/warden pocket 90% of your salary.

Is there any documented evidence of this happening?

EDIT:

https://www.theatlantic.com/business/archive/2015/09/prison-...

http://www.motherjones.com/crime-justice/2015/06/private-pri...

http://www.motherjones.com/politics/2016/06/cca-private-pris...