Build the biggest outbuilding you can afford and put tall ceilings in it too, it's cooler that way. You are going to want to put other stuff in it so you might as well have the room. You are also going to want a place to service the tractor and doing it on the shop floor is much nicer than the ground. So it really depends on your budget.
If you are just looking to store it and keep it out of the weather I see lot of folks do a three sided shed with a dirt floor. Since your in NC, I do not suspect you get much snow so rain is your biggest problem. If you do this then I would give your self about 4-5' past the length of the tractor with the implements off and build three stalls, one for the tractor, one for the FEL and one for the BH. A full fledged shop though is a much nicer way to go though.
If you are just looking to store it and keep it out of the weather I see lot of folks do a three sided shed with a dirt floor. Since your in NC, I do not suspect you get much snow so rain is your biggest problem. If you do this then I would give your self about 4-5' past the length of the tractor with the implements off and build three stalls, one for the tractor, one for the FEL and one for the BH. A full fledged shop though is a much nicer way to go though.