ISO mod that allows Sims to own multiple residential lots

Yes, there's a way for your sim to treat any residential lot as owned, but the question is how you want to manage properties. If you only want them to have ownership of the lot when they travel, then there's a really easy way to do that, but if you need to track bills and schedule household-specific events for multiple residential zones, then you might have a problem.

It would help if you tell us a bit more about why you want to do this.