Maybe not as much as you'd expect. I assume you are talking only about homeowner mortgage interest deduction, not landlord (investor), so that is a large chunk

Maybe not as much as you'd expect. I assume you are talking only about homeowner mortgage interest deduction, not landlord (investor), so that is a large chunk of the inventory that would not be affected. Also, with the temporary (TCJA) increase in standard tax deduction, fewer people than ever get any tax benefit for their mortgage interest, not to mention those who don't have mortgages because they've lived there so long.