Highest ROI investment, no risk.

[Nash Commerce]

Books from Goodwill.

Business, finance, psychology, trading, self dev.

$1 each. Fucking unreal.

 

[Certap]

How about the free YT and other online resources like free seminars? Does it count?

 

[bladee4r]

Books from Goodwill.

Business, finance, psychology, trading, self dev.

$1 each. Fucking unreal.

What do you mean by this?
Technically, Wikipedia would be the highest ROI investment if you were looking at one isolated service.