Can a landlord require 3 times the rent?

Yes, in most of the United States. No federal law sets or forbids an income ratio, so a landlord is free to require 3 times the rent as long as the same standard applies to every applicant. There is no "3x rent law" that makes it mandatory either. It is a business policy.

A few places limit it. Portland, Oregon caps the requirement at 2.5 times the rent, or 2 times for higher-priced units. California and Washington require landlords to compare a voucher holder's income only to the part of the rent the tenant pays.

The Fair Housing Act also applies everywhere: a landlord cannot use a tougher ratio for some applicants because of race, religion, sex, disability, family status or national origin.