Building Assets

Today I was thinking about how important it is to financial security to obtain real assets.  Now by assets I mean things that make money on my behalf NOT things of value that I use but could sell later.  It would be such a cool experience to purchase a forclosure home for real cheap then rent it out to great tenants for a profit every month.  It would be cool to obtain other types of assets that bring income too but I'm having a hard time thinking of other options and though the home is a great idea for income, it also takes quite a bit of money to get the home, even a super cheap one.  Any ideas?