Standard Conforming Loan amounts only, NO High Balance.Allowable Repairs or Renovations Repairs/improvements must be permanently attached to property and add valueCosmetic repairs only "Built-in" kitchen appliancesConversions:-Conversion of 2-unit to 1-units-Conversion of 1-unit to 2-unit by exception only.

That is that it takes a non-conforming loan to buy an expensive property.

I'd say that any lender saying 15% down is blowing smoke your way, perhaps some fee income, as an 85% LTV loan will be in a PMI or mortgage insurance requirement and the property is non-conforming, I'd say you'll be at least 20% down all said and done.

I'd step outside all that FHA and Conforming QM crap and search for a Stated Income ALT type program that does not require 25% equity to allow your to use the rental income for DTI.The State Income Alt loan programs are NOT No Doc as borrowers must prove the ability to repay the loan, just they have a lot more flexible guidelines for situations like yours.

There's also the issue of being able to sell a non conforming property.  2/1 is deemed functionally obsolete by todays standards and isn't particularly easy to sell on the retail market.  

In practice, they should conform to conventional mortgage and notes, but probably be as simple as possible.As a borrower, I am securing private financing primarily in two forms:1) Vendor Carry / Vendor take back - Financing of up to 5-years, preferably interest only, carried by the vendor on the property.  

You would be limited to local county Conventional Conforming loan limits on a one unit property, so not sure if that is enough to do it.

Currently there is a non-conforming bedroom along with a total of  1,000sqft of livable fully  finished and well lit from natural light living space, including a bathroom and laundry — and a kitchenette area.  

Conforming conventional full doc SFR non owner middle FICO 742 30 year cash out zero points for the next five minutes is 4.5.

They do generic conforming loans that get sold.