The loan on this house is $1,200,000.I moved in to my new primary residence by the end of the month.Starting July, my original primary residence was available as a rental and was being shown to prospective tenants.My new tenants signed a lease that began a couple weeks after showing, in July.To calculate my primary residence mortgage interest deductions, i'm using the following formula:650,000 / 2 = $325000 loan from January to June1,200,000 / 2 = $600,000 loan from July to December$750,000 limit / (600,000+325000 total loan value)  = 0.81 multiplier(0.81 * $X first house interest) + (0.81 * $Y second house) = total interest payed i can deduct from my primary residencedoes this look correct?

I'm open to all suggestions, advice, and criticism. 

Last month, I pulled the trigger on getting my first real estate property ever and decided to go with a 4 bed, 2 bath new construction to limit all the variables involved since I am still in college.

I have found that the profit margins are very low in this model if the house is in a C/D neighborhood because you are limited to the amount of rent you can charge for each room.

If you're a single mom with student loans, a car payment, and living paycheck-to-paycheck, then $20,000 would be devastating and a reserve is critical.

Knoxville specifically has some rules regarding STR in the city limits, county is a different set of rules (little more lax). 

Interviewing multiple GC's is the best way to operate, but make sure you are communicating to them that you may want to limit their scope of work as you may intend to SUB out some of the work ourself. 

That would reduce the FICA because you're over the limit.2.

I’d like to come in as a limited partner.

Reduced loan limits for investors might force many to seek alternative financing.