Given a lump sum of cash and annual withdrawal of a certain percentage of that cash (3% per year is safe, 4% is pushing it, 5% is a sure way to lose your money), you would need the following amounts of money to pay yourself $50,000 per year:

$1.67 Million @ 3% (1 / .03 * 50,000)

$1.25 Million @ 4% (1 / .04 * 50,000)

$1.00 Million @ 5% (1 / .05 * 50,000)

Put another way, if you have X Million, how much could you safely withdraw each year at 3% per year?

$1M: $30k / year

$2M: $60k / year

$3M: $90k / year

$10M: $300k / year

Keep in mind you will pay tax on these figures (15% Long Term Capital Gains tax if you're lucky, or more if it's regular income). And this does not account for inflation, so assume the value of money gets cut in half every 25-30 years.