If the developer does not stipulate the relevant terms of the gym in the contract, then whether the gym in the community is charged depends on whether the house where the gym is located is owned by the owner and who invested in the fitness equipment. If the owner of the gym house is a developer or property, and the fitness equipment is invested by the developer or property, then the gym may be regarded as a property service and a certain fee needs to be charged to the owner.
But if the developer clearly stipulates in the contract that the gym is open to the owner free of charge, then the owner can use the gym for free.
It should be noted that the situation in different communities may be different, and the specific situation needs specific analysis.