Is it possible to become a cop for only a few years?

Source: Bureau of Justice Statistics, US Dept. of Justice

In the Atlanta suburbs, starting pay is roughly $28K-$32K. My first department in central Florida now starts at $33K; I started at $9,600.

Obviously, this depends on the retirement system. However, I don’t imagine there are any systems that allow you to collect any benefits with less than 10 years service.

It’s not the army. You can just quit.

It depends on the department, and the contract with the union. When I was full time
they gave me everything, including 5 uniforms & then $300 per year allowance for upkeep. Now I’m on the job only part-time and I had to buy everything. I get $150 per year allowance while the fulltimers are getting upwards to $600. the allowance is no longer paid in cash like it used to be. Now it’s provided as a purchase order at uniform/equipment stores. This prevents one from drinking it up.
You can pretty much buy anything you want at the equipment store with the allowance EXCEPT shoes. By contract the department cannot provide shoes.

The biggest problem would be getting the job in the first place.

I can only tell you what it’s like in Wisconsin:

First, one must, by law, possess an Associate Degree in Police Science/Criminal Justice, or a Bachelor in anything else, or 60 fully accredited college credits.

Then you have to pass a written test. Then a medical examination. Then a Physical agility test. Then you have your first interview with the Police & Fire Commission.
After those interviews they create a list of eligible candidates. When a position becomes open, you get a second interview with the board & the Chief. Pass through that and you have to take a psychological exam.

If you fail at any of these, you’re out, and usually can’t apply with that particular department again for one year.

Get hired and then you have to go through the police recruit academy. 10-12 weeks, except for class A sized cities (like Madison & Milwaukee). Their academy is usually 22-26 weeks.

Getting on a larger department that hires more officers is easier (if you pass everything) than a small department that may go years without new hires.