The 30% rule and the income multiple
The most widely used guideline caps rent at 30% of your gross monthly income. Many landlords apply a related test in reverse, requiring that your gross annual income be at least 40 times the monthly rent — the same math from the other direction. If a unit rents for $2,000 a month, expect to need roughly $80,000 in annual income to qualify without a guarantor.
These are qualification thresholds, not comfort thresholds. In expensive cities where the 30% rule is nearly impossible to meet, spending 35–40% may be unavoidable, but every extra point of income committed to rent is a point unavailable for saving, emergencies, and debt repayment. Where you can, aim below the ceiling rather than at it.
The costs beyond base rent
Base rent is only part of your housing cost. Renters insurance, utilities not included in the lease, parking, pet rent, and application or amenity fees all add up. Building these into your budget before you sign prevents the common shock of an "affordable" apartment that stretches you thin once every monthly charge is counted.
Plan for the upfront cash as well. Move-in typically requires first month's rent plus a security deposit equal to one or two months' rent, and sometimes last month's rent too. That can mean three months' rent due before you receive a single paycheck in your new home, so confirm you have the reserves before committing.