How to Calculate Rental Property Cash Flow

What Is Rental Property Cash Flow?

Cash flow is the money left over after you collect rent and pay all expenses. It is the lifeblood of rental property investing and the primary metric most investors use to evaluate deals.

Formula: Cash Flow = Gross Rental Income - Total Expenses.

Positive cash flow means the property generates more income than it costs to operate. Negative cash flow means you are subsidizing the property out of pocket each month. Most investors require positive cash flow as a minimum threshold for any investment.

Cash flow is calculated on a monthly and annual basis. Monthly cash flow tells you what goes into (or comes out of) your bank account each month. Annual cash flow accounts for irregular expenses and gives a more accurate picture.

Income Components

Total rental income includes more than just base rent:

Base rent: The primary rental amount stated in the lease. This is your largest income source.

Pet rent: If you allow pets, charging $25-$50/month per pet adds meaningful income. With two pets, that is $600-$1,200/year.

Parking fees: In urban areas, dedicated parking can generate $50-$200/month per space.

Laundry income: Coin-operated laundry in multi-family properties can generate $30-$50/unit/month.

Late fees: While you do not want to rely on this, late fees are income when they occur.

Other income: Storage rentals, vending machines, application fees, lease renewal fees.

When projecting income, be conservative. Use market-rate rent (not the highest comparable) and do not count on ancillary income unless it is already in place. It is better to be pleasantly surprised than to have your business plan depend on optimistic assumptions.

Expense Categories

Accurate expense estimation is where most investors go wrong. Here is every expense category you need to include:

Fixed expenses (predictable monthly costs):

• Mortgage payment (principal + interest): Calculate using your loan amount, rate, and term
• Property taxes: Verify with the county assessor (and check for reassessment risk)
• Insurance: Get actual quotes from 2-3 providers
• HOA fees (if applicable): Verify current amount and any planned increases

Variable expenses (fluctuate month to month):

• Maintenance and repairs: Budget 5-10% of gross rent. Older properties require more.
• Capital expenditures (CapEx): Budget 5-10% for major replacements (roof, HVAC, appliances). These do not happen every month, but when they do, they are expensive.
• Vacancy: Budget 5-10% of gross rent depending on your market's vacancy rate.
• Property management: 8-10% of collected rent, plus lease-up fees (50-100% of first month's rent for tenant placement).
• Utilities (if owner-paid): Water, sewer, trash, gas, electric.
• Landscaping and snow removal: Varies by property type and region.
• Pest control: $50-$100/month for commercial service.
• Legal and accounting: Budget $500-$1,000/year.

Complete Cash Flow Example

Let us calculate cash flow for a $185,000 single-family rental:

Income:

• Monthly rent: $1,650
• Pet rent (1 pet): $35
• Total monthly income: $1,685

Fixed expenses:

• Mortgage (25% down, $138,750 at 7.0%, 30yr): $923
• Property taxes: $175
• Insurance: $110
• Total fixed: $1,208

Variable expenses:

• Maintenance (8%): $135
• CapEx reserve (5%): $84
• Vacancy (5%): $84
• Property management (9%): $152
• Landscaping: $40
• Total variable: $495

Total expenses: $1,703 Monthly cash flow: $1,685 - $1,703 = -$18 Annual cash flow: -$216.

This property is essentially breakeven. Whether it is a good investment depends on appreciation potential, your equity buildup, tax benefits, and whether you can improve income or reduce expenses. If you self-manage (eliminating the $152/month management fee), cash flow becomes +$134/month or $1,608/year, a 3.5% cash-on-cash return on your $46,250 down payment.