Parking lots and alternative investments

Does anyone know anything about investing in parking lots?  They seem like they would provide a pretty steady source of income, even if the returns are not incredibly lucrative. 

For argument’s sake, let’s say a midsize, flattop parking lot in a Midwest downtown.  What sort of capital does that require?  What range of returns can be expected?

My interest in parking lots stems from a more general concern, which is finding non-equity investments.  I continue to have (some) faith that in the long-term, equities provide a high-level of return.  But this is no reason to not diversity out of equities.  (On the other hand, I only own index funds, so perhaps I am already completely diversified and any further investment would overexpose me to one sector.)  The major catch is that I am just a young man out of college which only a few thousand dollars to his name.  So the more difficult question is: Are there alternative investments which don’t require one to be rich already?