SFH House Hack - Pros and Cons?

[Alan Ford]

Hi, so I live in CA and my state income tax wipes out my $10k allowable SALT Deduction. Leaving another $10k in property tax I can not deduct.

I am wondering what would happen if I had my friend come and live in my home with her two kids. We do it legitimately, have her sign a 12 month lease, pay fair market rent, actually send me checks each month etc.

Does this allow me to start making additional deductions as if my home was an investment property?

Side questions: -

1. does having this 12 month lease also help free up some of my Debt to income allowing me to secure additional mortgage financing for other property investment? 

2. What would happen if instead of my friend, it was my significant other but not married and everything else being the same? Does that even matter as long as not married?

Thanks