If Somebody Were To Cut You A Check Tomorrow For Any Amount,

$1mil or more to be safe ; especially if there is a reasonable chance your going to live 40+ years. but for someone who's 60 years old or so the could likely get by with less than $1mil.

Just to ball park things (for myself) and this assumes this is in ones pocket...

-$20k a year for 40 years = $800k (I would figure this would probably be a low end figure as things could be a bit tight)
-$30k a year for 40 years = $1.2mil (I would prefer not to go less than this to be a little safer though)
-$50k a year for 40 years = $2mil (I can't see a single person needing more than $50k a year for the foreseeable future as you should be living comfortable at this range for sure)

but it depends on ones age as if someone is like 60 or 70 years old they won't need as much as someone who's younger as I based my figures above on myself dying around 80 years old. but if someone is like 20 years old they will probably need roughly 60 years worth of $.

p.s. unless someone lives in some semi-rich area a single person likely won't need more than $50k a year for the foreseeable future to live comfortably enough as they can live in a decent area and eat decent food with a decent vehicle etc. probably with less but to be a little safer I would prefer the $50k a year to account for random crap happening as one could save a good portion of that $ each year so if ones health took a hit they should be safe with this especially if paired with a half way decent health insurance etc.