How large of a room do you need in order to be able to play a full sized pool table and have the arm room to pull the sticks back? That means adding the length of a pool stick at a light angle to each side of the table, I am not sure the size of the table or the sticks however.
The prices vary depending on quality. Check around online for a good deal. Or search craigslist like bushytails said if you want to try and find a 2nd hand table.
You need a lot of space for a full sized. I've played on scaled down tables and there just as much fun. You just can't hammer in a shot like on a full sized.