How long can a car with no plates sit on the street before getting towed?

I’m in Colorado if that matters......

There’s an auto shop a block away from my house and these people keep parking their cars (for a minimum of a week) in front of my house and on the side of my house. We have no drive way and 4 vehicles. They have left us 1 spot and only because my car was there.

I called the cops yesterday because the 2 cars have no plates and they issued them tickets.

How long can a car sit there with no plates before they’ll tow it? Will they even tow it?

It starting to piss me off because they take up all of the side streets and now in front of my house. What auto shop (they buy cars at auctions, fix them, then sell them) has no parking lot?! Seriously! Who decided that was a good spot to open one? Ugh.

UPDATE

The police finally called me back and they said after it’s ticketed they have 72 hours to move it before it gets towed.