Did it for decades, this is the first year I have not sold firewood in quite some time. This year I focused on some milling projects to build the hunting stands.
Having a white-collar job, I mostly did it to get some fresh air and stay in shape. Always all hardwood, and rarely got over $200/cord.
Before I got my hydro splitter (about 10 years ago), I split it all by hand!
When I used to heat my house with wood (before I established sources for wood) I used to buy a load of logs, cut them up with my 044 (my only saw for 18 years) and split 6 cord / year by hand to heat my house. Was good exercise and helped keep me in shape!
When I was doing firewood for others, I would remove trees for free if they let me take it for firewood. It was a lot of work, but everyone was happy, I covered my costs and earned "saw money", so house money was not used for my saw obsession! I currently have 14 runners and several incomplete projects.
As I've slowed down the last few years, the desire to build more saws has diminished ... I've got a pretty good collection and sometimes don't even use all of them in a given year.