I know a traveller family who picked up a homeless/drunk man sleeping rough,he has been on the farm for 15 years plus. He has his own accommodation on the farm and the family cook him three hot meals a day. He's very happy and in his 60's now. He has no family and regards himself as part of theirs now. He is happy and would never dream of leaving. I know his story is the exception rather than the rule. (Not that i'm condoning this btw)
I hadn't seen this one but a couple of years ago there was a story about a man who after having a breakdown and splitting up with his family fell into the clutches of people like this; he was hit by a car while walking to whatever work they hired him out to and was badly brain damaged. They continued to use him until he was eventually found dead. It was awful - I don't know if this is the same case as I'm not sure when the gangmasters were tried.
In the book 'Stuart, a life Backwards' by Alexander Masters, Stuart, who'd led an off the rails life (drugs, prison, rough sleeping etc) tells Alexander Masters of gipsies enslaving rough sleepers and making them work for them. At the time Alexander Masters laughs at the claim, and thinks it sounds far fetched. I don't know when that book came out (it's well worth reading) but there have been quite a few newspaper stories of that kind of enslavement of vulnerable people in recent years. As well as horrendous accounts of people trafficking of young girls for prostitution. Grim.