If you put living quarters and a mailbox on your retail lot, it'll function just the same. Just keep in mind that when you're out and about, if you click the "home" button the Sims will return to the empty home lot, so you'll have to bring them to the lot you want. I set up a bakery with a home above it and tested it with a family with toddlers. The toddlers were sent back to the empty home lot when they returned from daycare, but once I figured that out, it was just a matter of calling everyone to the bakery when I wanted them "home."
