From a thread here:
- The most accurate is to physically go to the place and politely ask the residents - making clear that you are considering buying and are trying to determine how many units are rentals.
- Online, if you go to the assessor's database if the owner's mailing address is different from the house address it's most certainly not a primary residence. This may mean it's rented out.
- Online, if you can see the property tax amount, many towns in Mass. have a residential exemption which applies to primary residences only. If the tax seems lower, then this is a primary residence.