#1. No idea. But, thinking down the line, you probably want to hold onto it. It'll add a lot more value to your property when and if you do decide to sell up and move on.
#2. I don't know the answer in terms of whether you're allowed to rent your space (that probably is up to your management co.) but it's definitely possible to rent your space, particularly if you're in the city centre.
You would need to check the terms of the lease for the apt. In my apt complex, the parking space must be sold with the apt. I do have the option to rent the car-parking space though.
Personally i think you would be mad to sell your car parking space! Its one of the main things people look for when buying an apartment. You dont know whats goin to happen in the future. Rent dont sell!!!!