Debt service coverage ratio lending qualifies on whether the rent covers the payment. Your personal income is not the deciding factor, which is what makes the fourth and fifth property possible.
An underwriter compares the rent to the payment. If the ratio works, the file works. For investors whose conventional guidelines ran out at four financed properties, this is the door that stays open.
Divide monthly rent by the total monthly payment including taxes and insurance. Above 1.0 means the property covers itself. Many programs go slightly below with compensating factors.
DSCR commonly allows title in an LLC, which conventional financing generally does not. If you are building a portfolio with liability separation in mind, that matters as much as the rate.