I will interject here... I don't think you fully understood the whole picture.
If you think your parents need 50k per year, the suggestion is to set aside around 10-15% per year now, and the amount set aside will grow. Once it reaches a critical mass, you could draw this down with little impact to current income. This combines the issues behind joetaxpayers posts and Skip's initial response.
50k per year for 20+ years suggests the amount needed might approach $1.25 M needed prior to assisting parents (assumes 4% starting withdraw rate). This would allow you to spend the 50k from earnings on the $1.25 M principal, without touching any salaries you make that year.To get to $1.25M, I see setting aside $10,000 per year for 25 years, earning a 10% return achieving that goal (so it takes you $250,000 of earnings over 25 years to have $1.25 M).
You could cut this another way to get to $1.25 M. You could set aside
20k per year and earn 15% returns for 20 years. You get the goal faster, but also need a much higher (and unrealistic) return.This goes back to understanding basic investing, knowing what variables you have control over (time, amount invested) and what variables are tough to control (return).
8% is a moderate return, requires some risk 10% is an aggressive return, requires more risk 15% is an obscenely high return, requires significant risk, real significant. And sustained risk over long period in this case. You might have better odds in Vegas.