Invest in an English dictionary - the site in your sig link has "Business Apportunity" as it's page title
For $50,you can't do much. But i would suggest you do some site flipping. Buy a site,maximize the site earning then resell it for 8x of the purchase price.
Yeah @mentos, good call... buy a cheap but a with some traffic or with some pagerank and maximize and then resell it! I would start an arcade game site and buy traffic and links