I think the term is "kick out," which forces the sim to find somewhere in town to live. The sim will take family funds up to §20,000, or more if you have NRaas Mover and have played with the settings. But you won't get to choose where that sim lives; they'll just wind up in a random house.
Try leaving the "Make Active Household" box checked in the right panel (for the sim you want to move, not the rest of the household), choose the empty lot you want, and only then switch back to keeping the main household active.
If this doesn't work or is being finicky, you can just click on the ground on the empty lot and select NRaas > MasterController > Add Sim, then add that particular sim. If you're running StoryProgression though, it may try to move the sim elsewhere, since an empty lot isn't considered a suitable house. So you may need to adjust your SP options; what you'd need to change will depend on how you've set up the options in the first place.
