If you're sharing common areas with your tenant, or tenants are sharing common areas with each other, it's important to clarify use of these areas and their boundaries in the rental agreement.
If you share laundry facilities with your tenant, are there certain days of the week that you want the machines reserved for yourself? This must be outlined in the rental agreement. Don’t restrict your tenant’s use of laundry facilities too much. Try for a schedule with some flexibility.
Secondary suites typically share electric or gas meters. Landlords usually expect secondary suite tenants to pay a percentage of the total monthly utility bill. Though reasonable in theory, this procedure has some foreseeable drawbacks.
How could you avoid all these problems? Calculate an estimate of utility usage by the secondary suite for the year and roll the average monthly cost into the rent. In other words, if you plan to rent the suite for $700 and estimate that your tenant will pay $75 per month for utilities on average, offer the suite at $775 with heat and electricity included. This way your prospective tenants will know up front where they stand with utilities.
This method is not without disadvantages. Because the tenant will not see the utility bill each month, there is a risk he or she will use utilities excessively or carelessly. Try reducing this risk by taking pre-emptive measures, such as serving a notice reminding the tenant that the rent includes a reasonable use of utilities, but that substantial overuse could result in a rent increase. Also, your lease agreement should have a clause prohibiting the tenant from installing any other major appliances or “energy eaters” such as second fridges without the express permission of the landlord.
In a legal multi-family apartment complex, the building code requires significant soundproofing between units. But the soundproofing found between the floors of a single-family home that contains a secondary suite is often inadequate. Even the best of tenants run the risk of being labeled noisy when there are inadequate sound barriers.
Even if these measures are implemented, the barriers between one living area and the other will never be up to the standard found in a multi-family building. If you want to earn extra income from secondary suites, be prepared to tolerate occasional noise or cooking smells.