I'll report something I learned based on my parent's experience. When they had a class C, they built two storage buildings - one at home and one at their lake property. Unfortunately when they upgraded to a 32' Dolphin class A gasser, both buildings had to be modified for height and depth.
Even then, the mods were made to accommodate their rig. When the time comes to sell the property, while RV storage might be a selling feature, it might not if the space is not big enough for the potential buyer's rig.
Always good to think ahead of possible future upgrades! It is likely easier/cheaper to build with growth in mind, rather than modify.