Is it reasonable to install a fence and require a toll for the residential property?

Under normal circumstances, the appearance of the house is not allowed to change, and so is the balcony. If closed, the property has the right to stop it. I think your property is just looking for an excuse to collect some money. Sealing the balcony is not a big deal, unlike smashing a load-bearing wall, so they won't care if you seal the balcony. They also have income. 100 yuan is not much, and ordinary owners will pay it. Both sides are very happy psychologically, and the property has no reason to charge you. But if you want to seal the balcony, you'd better hand it in.