If you have a permit for your house, you can call if someone is parked there, and the police will come and ticket/tow. That's my understanding of how it works. We have one, but we live in a neighborhood where everyone has driveways, so it's sort of superfluous (and it wasn't my idea to get it).

Street parking is fairly plentiful in most of Lowell, so I doubt it's an issue for most people, even in multi-unit buildings. Back Central is the obvious exception.

The only permit-parking neighborhoods I know of are right near UMass, where there have been problems with students parking on residential streets.