Well it's quite easy to move in several sims in one go without having to befriend them all. Befriend one from a household of several people, then pick the people from that household to go with them when they move in. The point of having more than one is to increase the value of paintings and sculptures. If the only thing (besides meeting needs, and not even that after you gain the moodlet manager) they do is paint, then the value of their paintings goes up and up and up, and likewise for the sculptures. Photography not so, but that way you have someone to take care of the cleaning and looking after kids, if you have any, once photography is maxed. Not only that, it's a tight squeeze to get the sculpting achievements before your founder's first birthday.