How do you mean 'use' cars? I assume you mean as decoration? I believe there are some decorative vehicles here and on other sites. I would suggest you ask in WCIF at our sister site S2C. You might also want to ask your question in the Nightlife forum there.
Locking, since your game is not broken.
I'm worried that my latest Salvation Army donation will result in homeless people looking like sluts from the 90s.