Good luck and enjoy.
I did a similar thing about 4 years ago.
10ft by 20ft.
Really enjoy the fact that I can paint and build down there, but also that I can leave a game set up, and no-one says “can I have the table back now for dinner ?”
I stained the outside of my one, and just yesterday, I finished staining it for a second time in four years. That bit, ain’t fun.