Photography is an art that satisfies my criteria for a hobby - there is an upfront cost (ongoing ;-)), but one can more or less go anywhere, anytime, at no cost.
My father's constant tinkering in photography during my childhood helped to pique my interest in my adult years. I first started dabbling (seriously) upon returning from an anniversary trip to Kauai where my dad let me borrow a nice camera (film) body and a few L lenses from Canon. I was hooked.
The evolution of digital photography was instrumental for me, as I no longer had to concern myself with the cost of buying and processing film, and could receive near immediate feedback to help solidify my recent learnings.
I started with Canon DSLR's in 2004, moving to full frame in 2013. I now shoot with cutting edge Sony mirrorless camera bodies and Zeiss lenses, and am enjoying the art more than ever.