These loans allow buyers to purchase a property “AS IS, WHERE IS”.Renovation loans are available in 30, 20- and 15-year fixed rate terms and can be used to purchase owner occupied, second home and investment properties.By time the renovations are completed, the home needs to be in move-in, live-in condition and conceptually ready to be resold without repair issues.Other Important Items to Know about “Conventional” Renovation LoansMaximum – Minimum Purchase/Upgrade Amounts:Maximum: Limited to 75% of the “after improved” valueOccupancy: Primary, Second Homes, Investment PropertiesUnits: 1-4 unit propertiesRenovation Term:The renovation term for this program is a maximum of 180 days.The Borrower(s) is responsible for the work being completed within the escrow period.

In my experience, you are thinking through this correctly.I've heard lawyers say, if the loan is in your name (which it has to be for conventional) and the deed is in the LLC, you aren't treating the business as an independent entity and in a severe lawsuit, the corporate veil is pierced and the LLC can be thrown out.I agree that one of the best defenses is to run your properties well. 

If you go with a conventional loan for the cash out refinance, seasoning periods are longer which draws out the process. 

Then refi into conventional or commercial loans, probably need a mix of lenders.

STR standard depreciation is 39 years @Andy Lanyi@Jonathan Cooper even if you take Bonus Depreciation as @Basit Siddiqi highlighted the remainder 40% will be prorated using the Half-year convention or Mid-quarter convention used in line with what you read in IRS Pub 946 

Trailers don't go up in value like conventional houses.In my opinion to get the true benefits of buying mobile homes you want to own the land underneath them.

@Rick Albert   I may get a lot of push back from the team but I split my utilities on my ADU the conventional way....each dwelling has its own meter for water, electric and gas. 

Quote from @Kevin Prasad: Hi all, I’m looking to negotiate a deal thats a mix of seller financing and conventional lending.

What happens if you buy the duplex with a conventional loan with the purpose to build an ADU to move in shortly afterwards?

The only reason conventional will not allow it at all is if you do not have a current housing expense.