The key concept is placed-in-service date. It is the date the property is READY to be rented. Usually it is the time you placed the advertisement.
1. 房屋保险要换成出租屋的保险。
and you should also require tenant to purchase renter's insurnace.
2. 自主到出租房的转换是在什么时间点发生?假如是5月租出去,是不是到2026年5月之前卖都满足2/5要求。
see above, placed in service date.
3 装修费用如何报税?
Any expense occurred before placed in service date is capital expenditure, can only be added to cost basis or depreciation basis. IBecause you spent X amount to get this house ready for rent, it's not on-going expense but initial aquisition cost that has to be added to cost basis for capital gain and deprecation basis.
4. 房屋如何折旧报税?
The depreciation basis is the cost of aquisition, not the value of the house at the time of you moving out. Therefore, the depreciation basis is the value of the structure (not land) when you purchased this property + improvement made before place the property for rent.
It's 27.5 straight line depreciation. For partial year depreciation calculation, use a tax software.
5. 如果第一年,租金不多,需要房屋折旧吗?
Yes. Don't be lazy. YOu have to keep track of depreciation and loss carryover in a spreadsheet througout the years of ownership so that you know how to deal with depreciation recapture at the time of the sale.