If I am not self employed, and I just rent a detached 2-car garage to a neighbor for his construction company, what kind of income is this?

The cost to rent the garage was $300/month for 6 months in 2017. I filled out a W-9, but have not receive a 1099.  I rent the house on this property. The home owners I rent from allow me to rent the garage.  The home owners do not receive any benefits or any of the income from the rental of the garage.  I use the income to help me pay my bills.