Magnets wouldn't work; they attach to iron which is far too heavy to make a space station out of. Even if you only put in walkways, you would double the weight of the station and quadruple the cost of launching the materials into space. Also, magnets don't provide any force on the body that would prevent muscle and bone loss.
Today and the coming years are not going to be about the whole nation being in space, but will be about the stepping stones to getting our children and their children into space.
We start with what we have and what we can do. We start small.
At the moment, centrifugal force is our only real option. A simple Stanford torus with a radius of about 40m spinning at 3 revolutions per minute would produce 0.4g: about the same as the gravity on Mars. The first to go would be selected as those who are not affected by motion sickness. That said, most people would be fine and would quickly become accustomed once in the environment. 0.4g sounds low but it would mean reasonably normal active movement, allow our bodies to function and work as intended and sitting and sleeping normally. Muscle and bone loss would be at a minimum compared to micro gravity. (I would still suggest extra banded resistance exercise like they already do on the ISS). This low gravity would also mean less supporting mass needed for the structure.
A good design of this size could have a population of a few hundred people, based on it being a working place where we are learning, doing science and gaining the experience to build the next size up.
Once running we could have a proportion of the habitat set aside for tourists. This will still be for the rich, but the rich would enable the rest of us to follow.
Remember I said small steps? I'm thinking 250 plus launches using SpaceX's next generation BFR just to build the structure.
This is something we could aim for and achieve in the next 10 to 15 years, once we have our best engineers and a big budget.
