The Number One Mistake New Landlords Make
Source: Texas Signals — aggregate county data.
A property cash flows $400/month on paper. Six months later, the A/C compressor dies ($4,500), a tenant skips two months of rent ($3,600), and you discover the insurance premium jumped 18% ($720). Suddenly your $400/month cash flow is negative for the year.
This happens because new investors budget for the mortgage payment and nothing else. They forget — or underestimate — the operating expenses that eat into rental income every single month, whether you see them or not.
The 50% Rule: Your Quick-and-Dirty Estimate
Before you do a detailed pro forma, the 50% rule gives you a gut-check:
Assume 50% of gross rent goes to operating expenses (not including the mortgage).
On a $2,000/month rental:
•Expenses: $1,000/month
•Available for debt service + profit: $1,000/month
•If your mortgage is $950/month, you cash flow $50/month
•If your mortgage is $1,200/month, you are negative $200/month
The 50% rule is deliberately conservative. It accounts for vacancy, maintenance, capital expenditures, management, insurance, and taxes — all in one simple number.
Actual Expense Ratios by Property Type
The 50% rule is an average. In practice, your ratio depends heavily on the property's age, condition, and type:
Newer / Recently Renovated Properties: 30-35%
•Built within the last 10 years or recently gut-rehabbed
•New HVAC, roof, plumbing, electrical
•Lower maintenance and capex reserves needed
•Modern insulation = lower utility costs (if you pay them)
•Example: A 2020-built single family in Kyle, TX
Standard Properties in Good Condition: 35-45%
•Built 10-30 years ago, well maintained
•Some deferred maintenance but no major systems failing
•Standard capex reserves (roof replacement in 10-15 years)
•Most single-family rentals fall in this range
•Example: A 2005-built home in Round Rock, TX
Older Properties / Multi-Family: 45-55%
•Built 30+ years ago
•Higher maintenance frequency
•Larger capex reserves needed (roof, plumbing, foundation)
•Multi-family has higher management costs and turnover
•Example: A 1970s duplex in San Antonio, TX
Value-Add / Heavy Rehab: 25-30% (Post-Renovation)
•After a full renovation, expenses reset to "new" levels
•But the first year may have warranty-covered repairs
•Budget conservatively until you have 12 months of actual data
Building Your Pro Forma: Line by Line
Here are the major expense categories with typical ranges for Texas single-family rentals:
Property Taxes (20-30% of expenses)
Texas has no state income tax, but property taxes are among the highest in the nation. Budget 1.8-2.5% of property value annually, depending on the county and any exemptions.
•Travis County: ~1.8%
•Harris County: ~2.1%
•Dallas County: ~2.2%
•Bexar County: ~2.3%
Insurance (8-15% of expenses)
Texas homeowner insurance is expensive, especially in hurricane-prone coastal areas and hail-prone DFW/Austin. Budget $1,200-$2,400/year for a standard single-family home.
•Inland metros (Austin, San Antonio): $1,200-1,800/year
•DFW area: $1,500-2,200/year (hail risk)
•Houston/Gulf Coast: $2,000-3,500/year (wind/flood)
Vacancy (5-8% of gross rent)
Even in strong markets, you will have turnover. Budget:
•5% in tight rental markets (Austin, DFW) = ~2.5 weeks vacant per year
•8% in weaker markets or for higher-end rentals = ~4 weeks vacant per year
This covers the time between tenants, marketing, and make-ready work.
Maintenance & Repairs (8-12% of gross rent)
The day-to-day fixes: leaky faucets, broken garbage disposals, appliance repairs, pest control, lawn care (if included).
•Newer homes: 5-8%
•Older homes: 10-15%
•Rule of thumb: $100/month per unit minimum
Capital Expenditures (5-10% of gross rent)
CapEx is the big-ticket replacement fund: roof, HVAC, water heater, flooring, appliances. These do not happen every year, but when they do, they are expensive.
•Roof: $8,000-15,000 (lasts 20-30 years)
•HVAC: $4,000-8,000 (lasts 12-18 years)
•Water heater: $1,000-2,000 (lasts 10-12 years)
•Appliances: $500-2,000 each (last 8-15 years)
Budget at least $150/month into a capex reserve fund, even if you just replaced everything. Future you will thank present you.
Property Management (8-10% of gross rent)
If you self-manage, this is "free" — but your time has value. Professional management in Texas typically costs:
•Single-family: 8-10% of collected rent + one month's rent placement fee
•Multi-family: 6-8% of collected rent
Putting It All Together: Sample Pro Forma
Here is a complete pro forma for a typical Texas rental property:
Property: 3BR/2BA in San Antonio, $200,000 purchase, $1,800/month rent
Monthly Income:
•Gross Rent: $1,800
Monthly Expenses:
•Property Taxes: $367 (2.2% of $200K / 12)
•Insurance: $150 ($1,800/year / 12)
•Vacancy Reserve: $144 (8% of rent)
•Maintenance: $180 (10% of rent)
•CapEx Reserve: $144 (8% of rent)
•Property Management: $162 (9% of rent)
•Total Expenses: $1,147
Operating Expense Ratio: 63.7%
Wait — that is higher than 50%. Is this a bad deal? Not necessarily. Many Texas properties run 55-65% expense ratios when you include reserves. The 50% rule is intentionally optimistic to help you screen quickly.
Cash Flow Analysis (assuming 20% down, 7% rate, 30-year mortgage):
•Mortgage Payment (P&I): $1,064
•Net Operating Income: $1,800 - $1,147 = $653
•Cash Flow: $653 - $1,064 = -$411/month
This deal does not cash flow with 20% down at 7% interest. You would need to either:
1.Put more money down (reduce mortgage payment)
2.Negotiate a lower purchase price
3.Find a property with higher rent-to-price ratio
4.Accept negative cash flow and bet on appreciation
The DSCR Connection
DSCR (Debt Service Coverage Ratio) is how lenders evaluate rental properties:
DSCR = Net Operating Income / Debt Service (Mortgage Payment)
Using our example above:
•NOI: $653/month
•Debt Service: $1,064/month
•DSCR: 0.61 — way below the 1.25 most lenders require
To get a DSCR of 1.25, you would need NOI of $1,330/month, which means either:
•Higher rent ($2,477/month to hit 1.25 with current expenses)
•Lower purchase price (reducing the mortgage)
•Larger down payment
Texas Signals calculates DSCR automatically in the Rental ROI Calculator. If the DSCR shows red (below 1.0), the property loses money. If it shows orange (1.0-1.24), it barely breaks even. Green (1.25+) means lenders will like it and you will too.
Quick Reference: Expense Ratios by Property Age
•0-10 years old: 30-35% operating expense ratio
•10-20 years old: 35-40%
•20-30 years old: 40-45%
•30+ years old: 45-55%
•Multi-family (any age): add 3-5% for higher turnover and shared systems
Use these as starting points, then adjust based on the specific property's condition, location, and your management style.
Head to the Investment Calculators to run the numbers on a specific property, or browse Texas Signals' tax delinquent and pre-foreclosure listings to find potential rental acquisitions.
Source: Texas Signals — aggregate county data.
Source: Texas Signals — aggregate county data.