Does working for evil people make you evil?

No, even if an extremist libertarian might say otherwise.

Depends on your reasons and what jobs you're doing.

In a way.

If you are aware of the evil being done, it certainly can be. There is a possibility of trying to work for someone with the hopes of providing them a route to redemption. But knowingly and willing assisting an evil person in the acquisition of wealth and influence would be something I consider evil.

If you do not know of the evil, then it isn't really. You could still be causing harm, however.

Only if your work is helping their evil in some way and you're aware of it.