Self-Employed Careers

Can Sims do more than one of the self-employed careers at once from the Ambitions expansion pack? One of my Sims just became a self-employed inventor. I noticed when they have enough skills for others of those self-employed jobs it shows more of them under jobs on the phone or newspaper. If I wanted him to do both inventing and sculpting and I told my Sim to do another one of the self-employed jobs when they already had one would it let me do another of them or try to replace the first one with the second one?
I gave him the lifetime wish where they have complete the inventing skill, sculpting skill, and the painting skill. Once I move him into his own house I want to put an inventing table and a sculpting table and work on both of those. To get promoted in these self-employed careers they have to sell a certain amount of Simoleons worth of the things they make. It works fine to sell them from their inventory but it just doesn't feel very fulfilling that way so I wanted to try having him sell them to the Consignment store but for some reason when I told him to go to a community lot neither the scrap yard or the consignment store showed up to go to them. I know I had placed both of them in the neighborhood, so I'm not sure if they some how go replaced by houses in the neighborhood or what but I will have to check next time I go into the edit town mode and put them back into the neighborhood if they did some how disappear out of the neighborhood.