A friend of mine did the TNT century ride in Tahoe this year, and his efforts are what inspired me to get back into biking. I'd like to do a charity ride next year, and I have a few general questions about fundraising and the differences between the organizations.

I've noticed that the Livestrong rides and at least some of the MS rides have really low minimum fundraising amounts (like $250), but the TNT rides and some of the others have much higher minimums, and I'm wondering why. Does some of the $$ go towards the participant's training and airfare? Are there other things it goes towards, or is it all going to the charity? Are there things I need to know (hidden expenses, things I'll have to plan for) with the events with lower minimums? How does it all work with these events?