1.rental property: mortgage interest allocation and percentage of the income and expense. 2. rented number of days vs personal use vs vacant days calculation.

[1201houz]

rental property mortgage interest allocation

rented vs personal use vs vacant

[pk]

What is the question ? How can we help you ?

[1201houz]

how to allocation mortgage interest for co-owner rental property and mortgage is under one owner

[pk]

Assuming that the co-owner is not related and that you two do not have formal partnership ( if a partnership then you have to issue K-1 and partnership return ), you allocate income and expenses on ownership percentage and issue  a 1099 to the other person.
However, if this informal, it may be easier just to put everything on the person whose SSN appears on the Mortgage document and the title and settle the gains/ losses after tax , with the other owner.  
Suggest you see a tax professional  and form a legal partnership -- this will only get more problematic over the years ,especially when you dispose off the property
In the meantime, file a request for extension
That is my view