first suggestion... stop cross-posting to multiple sections on the same forum!
Like others have said... and some research will show...
-lots of hard work depending on investment in equipment
-need a way to deliver firewood to customers
-never short a customer... it's a fantastic way to NOT generate repeat business.
-you can do minimal investment (chainsaw, splitting axe, rent a log splitter for a weekend, buy a load of logs... essentially do it all by hand)
-you can do higher investment (multiple saws, heavy duty splitter, small sized 'processor', buying loads of logs and having a place to cut/split/store/dry wood... truck w/ dump trailer)
Don't forget about all the costs of maintenance... spare bars/chains/oil/gas, oil changes for a wood splitter, maintenance on the truck... beating up on the same truck you rely on for delivering is not a smart idea.
As for starting a business... best to start small, build the business as you build a clientelle. No point investing $200k+ and processing 100 bush cords of firewood in the first year if you won't be able to sell it all, deliver it all, maintain customer relationships, etc etc. Have you got a truck... borrowing a buddy's isn't gonna work for this. I'd never lend my truck to a friend so he could overload it with firewood just to make a few bucks. Have you got a saw? A $100 saw isn't gonna process a large volume of wood...it'll be slow. Expect to invest several hundred for a "small" saw... 50cc+.
Have you got a place to store all this wood? Easily accessible by truck/trailer in the dead of winter, wet spring, etc.
How much $$ have you got to invest? Are you planning to go the route of filing taxes, registering the business, etc... or just selling firewood on the side?