Sorry. By no real estate, I meant no rentals. I know this is a very difficult thing to answer as there are hundreds of variables. I was more just curious if anyone had a number. Something like, $5M would get me $100k for 50 years.
Historically, most people used the 4% rule to determine the amount of investments needed for retirement. This is based off the Trinity Study which was published in 1998 where they looked at historic returns (back to 1920 I think) for the US stock market and evaluated the success rates for a 30-year retirement depending on when you retired and what returns you could have taken without running out of money.
Nowadays, most people use the 4% rule because for the last 50 years the average stock market return has been 11% annually. If you account for 3% annual inflation, that gets you a real return of 8% annually, which leaves a 4% buffer for market crashes or high-inflation like we are seeing now.
First, You need to figure out what your estimated annual cost of living will be in retirement, which can be based off your current budget and if you expect to spend more or less in retirement. For simple numbers, let's assume you want to spend $40k annually in retirement.
$ invested = annual expenses / 4%
which is the same as
$ invested = annual expenses * 25
So if you wanted to spend $40k annually, you would need $1 million invested to safely have a 30 year retirement without reducing your principle. If you wanted to spend $80k/yr, you would need $2M invested.
This is why it is so powerful to reduce your spending and avoid the consumer-minded culture we see in America if you want to shorten your working career.
Here is a good calculator for the amount of working time you need depending on your current balance, retirement spending, and contributions.
https://networthify.com/calculator/...0&expenses=20000&annualPct=5&withdrawalRate=4