Two numbers decide whether a rental pays for itself: what the tenant pays you, and what the property costs you to hold. Everything else is detail.
Enter both numbers to see the result.
If you're weighing up a purchase, I can tell you what comparable units in that building are actually renting for, not what they're asking.
What to include in carrying costs
Mortgage payment: the full payment, principal and interest together.
Property tax: annual bill divided by twelve.
Insurance: a rented-out property needs landlord coverage, not ordinary home insurance. It costs more.
Condo fees, if any.
Utilities you cover rather than the tenant.
Empty months. A unit that sits vacant for two weeks a year costs you roughly 4% of the annual rent. If you want to be conservative, enter your rent about 4% lower than the asking figure.
Big-ticket repairs. A roof, a furnace, or an appliance isn't a monthly cost until the month it is. Positive cash flow is where that money should come from.
This is arithmetic, not advice. I'm not a financial advisor or an accountant, and rental income is taxable. Run the numbers past someone qualified before committing to a purchase.