Detached ADU and Backyard Cottage Builder in Tampa Bay
A well-finished 750 sq ft one-bedroom detached ADU in St. Petersburg or South Tampa currently rents for $1,400–$1,900 per month on a 12-month lease. Smaller 500 sq ft studios rent for $1,100–$1,500. Larger 900 sq ft two-bedroom units can clear $2,100 in strong submarkets like Old Northeast, Hyde Park, and Seminole Heights.
Against a $165,000 all-in build for a 750 sq ft unit at $1,600/month average rent: gross annual rent $19,200, operating costs $3,800, net operating income $15,400, cash-on-cash return 9.3%, estimated property value lift $80,000–$130,000, years to full ROI on rent only 10.7, years to full ROI on rent plus value lift 3–5.
Detached vs. Garage Conversion vs. Attached: Which Is the Right Rental?
At 700 sq ft: Detached ADU costs $130,000–$180,000, rents $1,500–$1,900/month, highest tenant privacy, highest appraisal impact, 9–13 month timeline. Garage conversion costs $80,000–$140,000, rents $1,200–$1,600/month, medium privacy, 5–8 month timeline. Attached ADU costs $100,000–$150,000, rents $1,300–$1,700/month, lowest privacy, 7–11 month timeline.
For a pure investment-return thesis, detached tends to win on lifetime rent collected, appraisal impact, and privacy — which is what lets you charge the upper end of market. Garage conversion wins on cash-on-cash return for the first few years because the initial basis is lower.
Florida's Rental Rules That Actually Affect Your ADU
State layer — Florida Statute §509.032(7): Florida preempts local governments from passing new ordinances restricting short-term rentals. However, regulations in place prior to 2011 were grandfathered.
City of St. Petersburg: ADUs can only be rented for 30 days or more. Short-term rentals under 30 days are permitted no more than 3 times in any 365-day period.
Unincorporated Pinellas County: No 30-day minimum on ADU rentals in most zones. Short-term rental allowed subject to county business-tax registration.
City of Tampa: ADUs in overlay districts can be rented without a minimum term restriction. Outside overlays, Extended Family Residence prohibits rental to non-family.
Hillsborough County: No blanket 30-day minimum, but individual community plans may restrict.
HOA layer: Some Tampa Bay HOAs prohibit any accessory rental regardless of what the city or county allows. This is a contractual restriction — check your covenants before you build.
Design Decisions That Drive Rent in Tampa Bay
Three factors separate a top-of-market detached ADU from a bottom-of-market one in the same neighborhood:
1. Natural light and ceilings: 9 ft ceilings rent for more than 8 ft. Window area above 15% of floor area noticeably improves tour-to-application conversion.
2. Private outdoor space: A small patio or fenced entry court is worth $100–$200 per month over an ADU with no private outdoor area. For tenants, the difference between a small apartment and a home is often a single door out to their own patch of grass.
3. Full kitchen, not kitchenette: Tenants pay market rent for a 30-inch range; they pay below-market for a two-burner cooktop. The incremental cost of a full kitchen vs. a kitchenette is $3,000–$6,000 at build and adds $150–$250 to achievable monthly rent.
