For the state itself? None.

For state employees (i.e. representatives, judges, etc.)? Some get kickbacks.

See: https://en.wikipedia.org/wiki/Kids_for_cash_scandal

See: https://www.nbcnews.com/news/us-news/dhs-contractors-told-wh...

Alas, the "kids for cash" scandal was such a big news event that it dominates the results for any search you'd do on the subject of private prison corruption, but it's hardly the only example.