One key differentiator is first time investor vs. first time homebuyer - it will be much easier to qualify as a first time borrower for an investment property loan if you own a primary or at least have done so recently

My question is, if I intended to use the main house (over 51% of sq ft) as the primary residence, is there a way to use FHA or any residential lending?

.- who lives in primary unit?  

I have my primary residence that I have about 450k of equity in.  

It will cover whatever happens for your rental and your auto even your primary residence.

So you couldn't sell multiple primary residence and take a 250k deduction on each of them?

We moved forward with a construction to primary mortgage loan after doing necessary diligence. 

Hi Dane,You can sell now and seize the opportunity the primary residence exclusion from capital gains tax offers.

The primary lesson from this project was the importance of thorough planning and execution in renovation projects.

The primary calculation is based on X% of purchase price (depending on lender policy and borrower credit/experience) + 100% of rehab (normally).