I have heard that paying off your rental is not necessarily the best choice because of the deductions it allows for, but given the type of loan this house is mortgaged with, is it even possible to buy another home together and start renting this one out when I have a FHA loan on this one?

I'd start by talking to a mortgage broker/loan officer to find out how much you're qualified for. 

They also receive information on operational expenses through one of their loan servicer partners but I don’t find that to be entirely accurate.

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. 

Depends on your goals. refinancing is basically starting over with a new loan.

A bridge loan might be your best option here.

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

I make secured and unsecured loans Loan amount: $2,000.00 – $20,000,000.00 Loan duration: 6 months – 30 years INTEREST RATE: 5.95% ANNUALLY Loan purpose: ALL Loan Type: ALL LTV: 85-95% NO PRE-PAYMENT PENALTY, FAST AND RELIABLE FINANCING.

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

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.