Fastest option would be to sell it to an investor, and they either pay cash for it OR if it would qualify for a DSCR loan (for rentals) it can close in 25-30 days. 

You can also run your STR in your personal name or elect to start a company that operates the STR i.e. branding.If you do not qualify or for some other reason do not want or cannot qualify for conventional financing, you will likely have to go to some sort of DSCR or other business purpose loan route, and they will actually require you to put it into an LLC.

I also thought about just taking out an FHA loan (since my wife and I both have 750 credit scores) and buying a house and renting out my mobile home to cover the mortgage.

Are you looking to dive into the world of fixing and flipping houses but find yourself stuck on securing funding?

Option 1: I was thinking she gets her $650k, she holds the note on a 40 or 50 yr amort loan.

I am struggling to find any lenders that will do a line not a term loan.  

In such situations, a bridge loan to rehabilitate the property followed by refinancing becomes necessary.

Sold to a Veteran who used a VA Loan Lessons learned?

@Cliff DurrettIn some instances the first will take a discount to give the second some money, but in this instance they are so underwater I don’t think the second will approve this as they are basically getting wiped, and they have much higher BPO’sAlso be aware the lender may satisfy the loan but not release the debt, meaning they will allow for short sale but then get a judgment to have the balance of Debt validated and still owed

They can push a DSCR loan into negative cash flow territory which makes the rates even worse.