Go>Play Magazine has a six-page preview of Vice City Stories, it includes some new screenshots, as well as further details on the empire building feature.
A car is parked outside of each building that you can obtain, destroying it initiates an attack on the gang currently running it. To successfully acquire the building Go>Play say you must kill everyone outside and inside the building, furthermore it will not go up for sale until you "wreck the place."
After you choose what type of business to set up, and its size, the actual building takes around 2 game days to complete. After this you can save the game there and "make changes" to the business via the notice board.
You will have to work for the business as well, as it won't run entirely by itself, additionally you get a "pimped out" car (what type depends on the business) permanently sat outside the place.
Go>Play also suggest the soundtrack is just as good as Vice City's, which is great since Vice City still has probably the best game soundtrack in the world.
You can see scans of the mag over at the GTAForums topic thanks to Rockyfella.