Several options you can explore to get the down payment capital: Solo401k; HELOC on personal residence or from equity of the SFR; Cash Value Life Insurance Policy; Business Credit; Private Lenders, to name a few.

“ cash flow returns” almost always compare horribly to a simple bank CD after you deduct for insurance, prop taxes< vacancy, capex, prop management (or your personal time.) etc etc etc. 

Got insurance involved and use that money to remodel the entire inside, and add a new roof.

And given #3 above, it leaves about 20% of rent for all other expenses like property tax, insurance and other PM expenses like leasing fee, eviction fee and other minor expenses like for e.g landscaping, pest control etc.

This was the first property we carried flood insurance on, during our project.

The bay area has many old houses so be aware of what it will take to being them up to code and meet insurance requirements.

Work with your commercial lender/insurer/lawyer/personal banker and see if they know of any interested parties.4. 

But if you have a cash buyer who is specifically looking for income property, and even more specifically a vacation rental property,  I firmly believe that there is a value add from having a working STR there.

Before you close, can the rent from your buddy and the midterm tenant cover your mortgage, taxes, insurance, plus a bit extra?

I'm a firm believer that we can't ask for anything without giving A LOT first.