I started off with a young adult couple. They were both in the police career and eventually split up to do their lifetime wish careers. At one point I did get a Police Cruiser for each sim. I sold one and kept the other until the sim wasn't in the police force anymore and sold the second.
Each sim is a senior, but one died of old age and the other is older than dirt about 110 days old as a senior but the grim reaper came and my dog begged for the sim to come back *forhead smack*.
Anyway, I check my inventory every now and then to sell stuff I don't need anymore and i had like 10 Police Cruisers and homework from someone else's children. There were about 5 pieces of homework and all were 0% completed. I had adopted a child and she was a teen by this point. I got lots of simoleons for the Police Cruisers and I also sold the homework. (lol) I don't know why I had about 10 Police Cruisers and my only guess is that my adopted sim either stole the homework or they gave it to her to do instead of them doing it. It's never happened and I don't think it can. Probably just a random glitch.
Anyway, it was funny.