[kranner]

Income from interest is as passive as it gets.

[quickthrower2]

But the catch is devaluation of the principal.

[charlesdm]

Not if you account for inflation in your calculations..

[tluyben2]

Which you should...

[quickthrower2]

Then you end up with very little (if any) income :-)

[marketgod]

Not really. Look up lazy portfolios by Bogleheads. If you continue to invest it can grow for you. I mean not at insane levels but definitely a decent return for many.