How much does it cost to add a spouse to property deeds in Kentucky ?

Nothing, unless you sell any part of it to her. Then there's a 'revenue tax' or 'stamp tax' based on the amount.
There might be a filing fee.

Whatever the official who records deeds (often the clerk of court) charges as a recording fee. You can get a quitclaim deed form online.


... Then there's a 'revenue tax' or 'stamp tax' based on the amount.
...

Yes, that too. Depends on the sales price, normally.

Such costs are usually by county. So I would check with the County Clerk's office. Usually there is no cost other than filing fees to add a spouse. To add another person might incur other costs related to a sale.