When I was in consulting, it was part of our regular contact language that we had verified backgrounds and that we wouldn't place a felon on site with a client. A surprising number of clients even outside banking, finance, government, etc made a point of enforcing this language, even conducting their own background checks.
Freelancing was the approach I saw some people do successfully, but there were lots of projects we couldn't put them on.
We even saw clients that refused anyone who had even a misdemeanor, at which point I discovered how many of our consultants had misdemeanor DUIs or arrests for various non-violent reasons.