The apartments will be managed and serviced by the co-op. The apartment owners will be paid rent and maybe dividends from the co-op.
Apartment owners can stay as much or as little as they like.
Owning an apartment there could be a good permanent base for nomads. Benefits include mail forwarding/handling and taking advantage of financial residency in Bulgaria (10% income tax).
If your lifestyle is nomadic, it will be a great place to visit and invest in - no need to live there permanently.