We assume you have a house and you consider selling it and investing the money, say $300,000, in some "safe" investment at, maybe, 5%.
You're considering renting instead of owning.
A condo requires no maintenance ... and that's just fine with you, if you can afford it
You'll have your normal take-home / after-tax salary (from whatever sources) PLUS income from the sale of your house.
You ask yourself:

• Should I rent the condo, knowing that the income from that $300,000 will help pay the rent?
• What percentage of my after-tax income will my expenses be?
• If I keep the house (so I don't have that $300K to invest), what's that percentage?
• Anybuddy got an envelope so I can do back-of-the-envelope calculations?

Here's your envelope:

Rent a Condo: Annual EXPENSES: Condo/Apartment Rent (if you rent a condo) = $ Gas / Electricity / Water = $ Phone = $ TV = $ Water Heater Rental = $ Condo Insurance = $ Car Insurance = $ Car Gas & Repairs = $ Property Repairs & Maintenance = $ Groceries = $ Vacations & Living it Up = $ Other Stuff I may have forgotten= $ Annual INCOME: After-tax Income / Salary = $ Investment from Sale of House = $ Return on Investments = % Tax on Investment Income = % Total EXPENSES as a percentage of your Total After-tax INCOME = %

Keep the House: Annual EXPENSES: Property Taxes (if you have a house) = $ Gas / Electricity / Water = $ Phone = $ TV = $ Water Heater Rental = $ House Insurance = $ Car Insurance = $ Car Gas & Repairs = $ Property Repairs & Maintenance = $ Groceries = $ Vacations & Living it Up = $ Other Stuff I may have forgotten= $ Annual INCOME: After-tax Income / Salary = $ Investment from Sale of House = $ Return on Investments = % Tax on Investment Income = % Total EXPENSES as a percentage of your Total After-tax INCOME = %

P.S.
There's a more sophisticated calculator spreadsheet here.