On ChrisHallquist's post extolling the virtues of money, the top comment is Eliezer pointing out the lack of concrete examples. Can anyone think of any? This is not just hypothetical: if I think your suggestion is good, I will try it (and report back on how it went)
I care about health, improving personal skills (particularly: programming, writing, people skills), gaining respect (particularly at work), and entertainment (these days: primarily books and computer games). If you think I should care about something else, feel free to suggest it.
I am early-twenties programmer living in San Francisco. In the interest of getting advice useful to more than one person, I'll omit further personal details.
Budget: $50/day
If your idea requires significant ongoing time commitment, that is a major negative.
The one study I've seen that looks at the net health effect of cycling came to the conclusion that cycling is a net benefit. Loads of bicycling advocates promote this to suggest that cycling is in general a net benefit for you health. Unfortunately for North Americans, the data in the study came from Europe. Cycling is much safer in Europe. I am not aware of any analysis using data from North America, and I'm unsure whether such an analysis would come to the same conclusion.
With this being said, I ride a bike for transportation. I read studies on safety and actively try to minimize my risk. This includes minimizing my mileage, as the risk is per unit distance. So far, so good. I haven't been in a real crash yet in 4 years of commuter cycling, though I've had plenty of close calls. Worst I can say is that I did once hit a pothole and fall over, but there were no lasting effects.