I knew someone who used to work for a company where they had a policy to only hire developers on work visas. The management treated them as indentured servants

I knew someone who used to work for a company where they had a policy to only hire developers on work visas. The management treated them as indentured servants rather than employees, using the threat of losing their visas and making them pay ‘legal fees’ as tools for coercion. The guy I knew only got out because my then employer promised to endorse his visa and deal with any legal stuff.