I bought a retail store for my sims paintings. Most are masterpieces, with a few excellence thrown in. I do however, have other things in the store in between my sims painting enough. After they have about ten or more paintings, she goes to the shop to sell them. I mark everything as high as it goes and she sells out of the paintings by the end of the day, which is quite a hefty sum. I finally have a restaurant that is actually making money now, still a few glitches, but otherwise, it runs well. Just start out small and try to run a retail yourself at the beginning to save on salary. As you start making more money, then buy the smallest price advertisements. It takes a lot of time to run a business.