A lot of expensive hobbies don't have to be expensive. I'm a musician, and I have spent thousands of dollars on musical equipment but realistically, if I weren't going to play out, or record high quality songs, you can get away with just a $200-$300 guitar (you might even be able to go lower. Cheap guitars are crazy good these days), a used amp, a tuner, and a cable. With that alone you have a lifetime of entertainment and challange, and the most expensive long-term cost is your strings. It's honestly a steal in term of cost to entertainment ratio.
Now. That said. The real challenge is not falling into GAS (Gear Aquisition Syndrome), which is a real challange. And if you become even mildly capable on guitar you're probably gonna wanna play live and record too, so, easier said than done, but it doesn't have to be expensive.
