I have had several of them make lattes when they had the original kitchen, so you don't have to have an upgrade for them to be able to make them. When I first added version .04 to my game, almost all of the peeps 14 on up were trying to make them. I haven't yet added version .05 and I may not as I'm happy with .04 still.

The only way to make money faster than having them work for it and get promotions is to have them sell collectibles. Well, besides getting a random event where they get money -- which isn't something you can make happen anyway.