We have lived in our basement for 14 years.
Yes, it's finished. Inside, you'd never know the difference.
As per the roof, we used a lean-to style with plain metal roofing. I would reccommend using screws. We used nails and over the 14 year period, I've been up there a few times hammering nails back down and resealing seams. Eventuall put in some screws. We have a drop ceiling inside and there are a few 2x4 pannels that need to be replaced because of stains from leaks we've had here and there.
Hopefully, this spring, we'll be ready to do just what you were talking about, tear off the roof and build on top.
If you can tough it out, it's a good thing. We actually own our home, NO MORTGAGE. We have actually paid for things as we've gone along as opposed to getting ourselves into debt way over heads. WOW, what a concept !!
Well, hope this info helped. It was a very inexpensive roof and we shoul be able to either use the metal on a shed or garage or sell it to someone who will.
Good Luck to ya .... By the way, have you by any chance ran accross the pros and cons threads to A-frames. I saw it briefly on this website due to a search render, but can't seem to get back to that reading. If you have, or find anybody that has, give a shout would ya?