"Centripetal" section of Wiki article on Artificial Gravity says:
This form of artificial gravity has additional engineering issues:
Kinetic energy and angular momentum: Spinning up (or down) parts or all of the habitat requires energy, while angular momentum must be
conserved. This would require a propulsion system and expendable
propellant, or could be achieved without expending mass, by an
electric motor and a counterweight, such as a reaction wheel or
possibly another living area spinning in the opposite direction.
Extra strength is needed in the structure to keep it from flying apart because of the rotation. However, the amount of structure needed
over and above that to hold a breathable atmosphere (10 tons force per
square meter at 1 atmosphere) is relatively modest for most
If parts of the structure are intentionally not spinning, friction and similar torques will cause the rates of spin to converge (as well
as causing the otherwise stationary parts to spin), requiring motors
and power to be used to compensate for the losses due to friction.
A traversable interface between parts of the station spinning relative to each other requires large vacuum-tight axial seals.
first bullet: Keep it spinning. Use photon momentum to spin it up and/or down. Get energy from solar panels.
... second bullet: Build it strong
... third bullet: maintain physical separation via magnets to reduce friction to near-zero, OR completely separate the spinning part from the non-spinning part, then spin down the spinning part if/when docking is required.
... fourth bullet: See third bullet, part 2, and/or exit to other parts of the system through a tunnel which goes parallel to, and is concentric with, the axis of rotation... kind of like the hole in a toilet bowl. Use a magnetic bearing for the seam. OR, go between via spacewalk.