According to Apartments.com, the amount of income spent on base rent should be no more than 30 percent of earnings after taxes. Base rent does not include any utilities that must be paid in addition to rent.
Visa's Practical Money Skills for Life website points out that some areas may have a higher standard of living that will require a higher percentage of monthly income applied to rent. Any adjustments made to the percentage amount should be accounted for elsewhere in an established budget. If rent is higher for example, then the difference above 30 percent should be deducted from other, more expendable areas.