Is it reasonable to pay the property fee just after the new building is handed over?

The property fee is calculated from the date of repossession. If you don't live, you still have to pay the property fee, but some property companies can confirm that your room is vacant, which depends on the property company in your community.

If the house has not been closed, but the closing date of the contract has arrived, it is also the beginning of calculating the property fee. And you haven't closed the house at the end of the contract period, then you have violated the relevant provisions in the purchase contract of the previous property. So I suggest that you accept the house normally, but negotiate the property fee with the property company.