Whoever is in your playable Sim's "Most Acquainted List", is likely going to show up to your doorstep, often. Even relative strangers, that your Sim has met recently, will likely show up, from time to time. Sometimes, they all show up on the same day, up to seven at a time. What I sometimes do, to minimize that, is put a bed & facilities on an unused lot & spend a few days there. Make sure there are no doors, so your Sims can access what they need. You can put up walls for privacy, though. This often seems to reduce walk up visitors.
Just a thought