Maybe. If I understand you correctly, you're talking about selling the information that you're ready to leave a 100% privately owned/operated off-street parking space to someone else who is looking for such a space and is willing to pay the parking fees to the owner/operator, as well as paying you for the tip about the vacant space.
Basically it would depend on whether the parking space vendor's contract with motorists sought to prohibit such arrangements as a condition of use. Of course that's a rather heavy-handed unilateral tactic, but you're not legally required to enter into a parking arrangement with them so if you don't like their terms and conditions, you don't park there in the first place. The mere inconvenience to you of having to seek other parking or transit options doesn't constitute a property interest, so you have no particular claim on the fairness of the T&C. Same logic that allows parking lot operators to disclaim liability for theft/damage to your vehicle.
Basically it would depend on whether the parking space vendor's contract with motorists sought to prohibit such arrangements as a condition of use. Of course that's a rather heavy-handed unilateral tactic, but you're not legally required to enter into a parking arrangement with them so if you don't like their terms and conditions, you don't park there in the first place. The mere inconvenience to you of having to seek other parking or transit options doesn't constitute a property interest, so you have no particular claim on the fairness of the T&C. Same logic that allows parking lot operators to disclaim liability for theft/damage to your vehicle.