Basement apartment

A basement apartment or basement flat is an apartment located below street level, underneath another structure—usually an apartment building, but also homes and businesses. Cities in North America legally define them as an accessory dwelling unit or "ADU". Rent in basement apartments is usually lower than in above-ground units, due to deficiencies common to basement apartments, which are often cramped, and typically noisy, especially due to passing traffic. They are also particularly vulnerable to burglary, especially those with windows at sidewalk level. In some instances, residential use of below-ground space is illegal, but practiced regardless.

Owning a home with a basement apartment can be an investment, both providing an income stream and adding to the value of the property.