Every tenant is a source of risk for a landlord. They can cause damage to the unit, use utilities that the landlord pays for and get into conflicts with other tenants. You probably take care to screen potential tenants for problematic behaviors.
A history of evictions or a major criminal background will likely give you pause when considering a new tenant. Unfortunately, not everyone who lives in one of your units will fill out an application and be on the lease.
One parent might apply and not disclose any information about their live-in romantic partner because of their criminal record. A tenant may also have initially been honest but has since taken in a sibling or started a new relationship with someone who now seems to live at the rental unit. What can you do when a non-tenant starts living at your property?
Document the situation before you address it
Whether you have heard complaints from other tenants or noticed that someone who doesn’t live at your apartment seems to leave every day at the same time when you arrive for maintenance, you will have some factual reason for assuming that an individual has started living in the unit without your permission.
Having specific times and dates to reference when a person leaves or how long their vehicle stays in shared parking spaces can be enough to prove that they have utilized the facilities far more than a casual guest would. You want to have proof of the occupancy or inappropriate visitation habits before you try to address the issue with your tenant.
What does your lease say?
The first thing you need to confirm before you take any steps is how your lease addresses non-tenants staying at the property. Most standard leases include restrictions on how long a non-tenant can stay in the unit. Some landlords will not allow someone to spend even a single night, while others may restrict such stays to no more than four or five nights in a single month.
Some landlords have a zero-tolerance policy for such behavior, meaning that they can terminate the lease and evict the tenant for bringing in an undisclosed roommate. Others may have a per-day fine included in the lease that far exceeds the additional rent for a second adult.
Once you know what your lease says, you can then send your tenant formal notice about the issue and ask them to resolve it immediately. Many tenants will be quick to resolve the matter. They may even agree to add their new romantic interest to the lease. Others may stop violating the lease instead.
If a tenant refuses to take appropriate action one way or the other, you may need to take them to court to either seek damages or to terminate the lease and possibly evict them. Consistent enforcement of lease rules regarding unauthorized visitors helps protect you and your property from violations by your tenants.