@DivinylsFan The trouble with inviting a uni sim to visit and then move in or marry is that the sims that show up as tourists are not full sims themselves, just mini versions with limited data attached to them. If you try to incorporate one into your homeworld, all kinds of things can go wrong, up to and including save-breaking corruption.
The better approach is to ask the uni (or foreign) sim to move in while your sims are still in the uni or vacation world, then bring them home. That way, you'll get the full version of the sim. Alternately, you could let NRaas sort it out instead. Since the new site looks like it's down for the moment (I'm sure it will be back soon enough, but I'm too tired to wait), here's the Wayback Machine's page from the old site describing how to import foreigners without damaging your game:
https://web.archive.org/web/20180118102610/http://nraas.wikispaces.com:80/Traveler+FAQ#Adding%20More%20Residents