Running costs a pair of shoes every now and then and extra laundry detergent but otherwise free. Like any other hobby you absolutely can spend tons of money on it but it's not required.

Runkeeper is a free app where you can log down your runs but a casio watch with stopwatch is good enough if you know the distance.

Also, contrary to what a lot of people think you don't have to push yourself, you can just be easy running (chill jogging) and still make massive gains in endurance, speed, physical health and mental health. Depending on your starting point brisk walking can be sufficient to get started and then transition to "let me just jog a bit" when you feel like it and still have massive gains.

You can even combine it with other hobbies like audiobooks, music and/or podcasts.

Running feels to me like "cleaning the pipes" of the body that's relaxing and makes the remainder of the day a bit more enjoyable.