The expenses incurred to prepare a room for rental are not tax deductible. Rental expenses are only deductible from the day the is available for rental on AirBnB.
These costs can be added to the cost basis of your property, which will help reduce capital gains at the time you sell the property.
Does it make a different that this room is currently unused and not part of the square footage of the house? I'm spending a substantial amount of money (25K) to put in a bathroom, kitchenette, separate heating/cooling etc. Is there is no tax benefit in the year that I incur the expense (if its before the room is available for rent)?
To confirm the only tax benefit I will see is when I sell the property because the expense is added to the cost basis of the entire property (which will in turn reduce my capital gains tax burden?)
I confirm that you cannot deduct these expenses and can only add them to your cost basis