This is from a rp on another board which I liked but fizzled really quickly :( this is just an outline, if anyone is interested I would love to have your input!
Your character is a witch/magic user living in a small town*. He runs a little magic shop and makes a living by selling spells and potions. Though his business and magic in general is legal, he's far from popular. In fact he's endured taunts and even violence because of his profession his whole life, though he'd never consider moving. There are still people that depend on him, and this is his home.
The harassment has started to get increasingly worse. The town's new mayor hates magic users and suddenly what little protection he had before his vanished. He's openly taunted in the streets, his shop has been repeatedly vandalized, he's received threats, and it shows no signs of stopping. He starts to fear for his safety, and with no one willing to help him he takes a drastic step- buying an ex arena slave to be his personal bodyguard.
Note: I could see this working in nearly any sort of setting, even a modern one. (the thread before actually took place in the 1920's) This would be a fight for dominance type thing at first, since MC isn't going to be very happy about the arrangement, and arena slaves are notoriously difficult to handle. After all, it's pretty difficult to make someone be a bodyguard. Magic might be employed to help keep him in line, or maybe YC is desperate enough to trade sex for protection?,
*revised- this could also work in a large city, if magic is stigmatized to an extreme degree.