We had 3 bids when we added 800 square feet of living space (family room, 3/4 bathroom, bedroom & kitchenette) and a 600 square foot attached garage. The high end of the bids was at $137,000 and the low end of the bids was just over $95,000.
I'd suggest you get 3 bids from 3 licensed and insured general contractors to get a more concrete idea how much it would cost. All reputable contractors will give you a FREE estimate.
Best of luck
It will cost between $150 and $450 per squre foot.
Surely you realize that "flooring" could mean Linoleum and it could mean Reclaimed Solid Cyprus.
You need to contact several contractors and get estimates:
This is a Real Estate site, by and for Realtors and their clients; I don't expect too many General Contractors to see your question.
Good luck and may God bless