People have been thinking about pseudo gravity in space by using a spinning space ship and using inertia and the centripetal force to cause objects and people to press against the outer rim of the station since 1903 (as far as I know this was proposed by the Russian scientist Konstantin Tsiolkovsky). Had to look that up in Wiki
This has been brought up again and again by people like Herman Noordung and Wernher Von Braun. The best example and the most complete idea is from Von Braun for his spacecraft for Mars. It was to be a rotating wheel with a diameter of 250 feet and 3 decks. It was to rotate at 3 RPM and would give one-third pseudo gravity for a crew of about 80.
The ISS was actually designed to be a micro gravity space station because there was still (and is still) so much to understand about the micro gravity environment and the effects of space on a manmade structure. So the ISS is built for the purpose its serving.
So here are the main problems with creating pseudo gravity by spinning a space ship.
1. It could get nauseating in that ship due to coriolis force. Nobody is really sure how humans will react. This can be countered a bit by making the ship big (which is what Von Braun did).
2. Its going to be very expensive to build this thing. In case you haven’t read in the various posts here we don’t have a heavy lift rocket right now (actually nobody has a heavy lift rocket right now). So imagine how many rockets you have to launch to put that much mass up there, and how many more rockets you have to launch to put people there to build that rocket.
3. Assembling and then pressurizing this monster is no easy task, I would actually call it a formidable task.
It is within the technical ability of the human race to do this thing right now, but it most certainly is not within the budget of any space program (not even all of them combined) to do this project. Basically the most complicated structure ever built in the history of mankind is the ISS (there have been more complicated things, but they were not in space), and it pails compared to this rotating space ship.