But how much will it cost?

This is a thing to consider.  I found a good post about fellow travelers and how much their trips cost.  Their per-person rates go from about $50 to $75 per day.  Sounds like a lot, but it's only $18-27k for a year.  ... which is less than I spend here in the States.

I think I can do it for the lower end of that range.  I plan to travel mostly overland, and Asia (besides Japan) tends to be cheaper than Europe, Africa, Australia, and North America.  (not sure about South America, I think it's comparable.)  I've budgeted $20k.  Course, I'll keep you updated once I actually start spending money.