How A Legal Basement Bedroom Increases Rental Income
Published August 14, 2026
For a rental property, a legal basement bedroom shows up in the rent roll the month it goes on the lease. 2026 HUD Fair Market Rent data for the St. Louis metro puts a two bedroom around $1,218 a month and a three bedroom around $1,568, roughly $350 a month or over $4,200 a year for square footage the basement already has.
For an investor renting a property instead of selling it, the ROI on a basement bedroom isn't the number you'd see at closing. It's the number that shows up in the rent roll the month a legal third or fourth bedroom goes on the lease.
According to 2026 HUD Fair Market Rent data for the St. Louis metro, a two bedroom unit runs around $1,218 a month. A three bedroom runs around $1,568. That's roughly $350 a month, or over $4,200 a year, sitting in a basement that already has the square footage to be a bedroom. It just isn't one yet, legally.
There's real value on the resale side too. In this market, we typically see a legal bedroom add $15,000 to $25,000 in appraised value, based on real jobs and real comps we've tracked here for more than fifteen years. But unlike the rent bump, that number only shows up once, at closing.
What Makes The Room Legal
The word legally matters more here than almost anywhere else in a home. A basement room can have a bed in it, a closet, and a coat of paint, and still not count as a bedroom on a lease or an appraisal. What makes it official is a code compliant egress window, sized so a person can climb out and a firefighter can climb in.
Hand Digging And Site Work
We hand dig every well we install. That matters most in tight side yards and fenced lots, where a machine crew would have to tear something out just to get equipment back there. For an investor watching a renovation budget, avoiding that kind of unplanned site work adds up.
Illinois And Missouri
The code itself doesn't change between Illinois and Missouri. What changes is how each jurisdiction handles permits and inspections, and that affects your timeline more than your bedroom math. Either way, the room isn't legal until the window is in and the inspection is passed.
Two Kinds Of Investors
We hear from both kinds of investors. Some are chasing a resale number and want the bedroom count to hold up on an appraisal. Others are holding the property and want the room to hold up on a lease, with a tenant living in it day to day. Either way starts in the same place. A room without a code compliant egress window isn't a bedroom yet. It's potential.
Frequently Asked Questions
How much more rent does a legal third bedroom bring in?
Using 2026 HUD Fair Market Rent data for the St. Louis metro, a two bedroom runs around $1,218 a month and a three bedroom around $1,568. That's roughly $350 a month, or over $4,200 a year, and it repeats every month you hold the property.
Can I list a basement room as a bedroom on a lease without an egress window?
No. A basement room isn't a legal bedroom on a lease or an appraisal until it has a code compliant egress window, sized so a person can climb out and a firefighter can climb in.
Will the install tear up a tight side yard or fenced lot?
We hand dig every well we install, so there's no machine access needed and nothing has to come out of a fenced or narrow yard to get equipment back there.