re: How much money invested/saved could allow you to retire?

The question posed is based upon you having everything currently paid off: House (whether its 200K or 500K), cars, etc..

All of your typical accounts payable would be typical monthly bills like utility, fuel, phone, insurance, etc. Add those up, plus your EOY property taxes/home owners insurance, and go from there.

Say, the total of these bills are $2K/month, so you have at least $24K just for that. How much would you want to spend per month in your retirement? Another 5-6K?

If its $6K, then that's another $72K per year and $96K total for the year.

If you had $2.5 mil and managed to receive a 5% return on it, you would see your $2.5mil stay at least $2.5mil in spite of you spending ~$100K per year.