@Flavia Vangelotti With your expressed concern for cash flow, I suggest considering a Debt-Service Coverage Ratio (DSCR) loan.

A bridge loan might be your best option here.

Though it is over 50% cheaperin my market, the price came in about the same although Reonomy isn't market-based but is limited with contact search, Reonomy has loan maturity data which co-star is lacking which is a big upside. costar has leasing data and is  also more accurate. 

You can also not improve your stocks and make them worth more.

Which will be best for down payment and which loan to choose.

Is it possible to refinance it with a fixed rate loan of some sort?

You are not taxed when you are taking out a loan. 

What are other questions we should discuss in advance.any advise, any sample document.Thanks look at 10 joint venture deals before you do one. talk to others in other markets. if he isn't smart enough to negotiate capital or JV deals or structured finance I wouldn't touch him. every cost should be fully transparent with their margin. similar structures with investors in columbus we are the general and everything is negotiable. he should also be qualified talk to a bank first. we take title in a single purpose entity we are the LP less than 20% and the qualifier and the main investor puts the cash and gets the loan, I'm also licensed and normally sell to out of state investors. 

30 yr fixed Vacation/2nd home loan with 10% down.

I prefer using my s-corp for loan/deed purpose.