You do that, it's going to be best place to start because I am betting from there you will seek how to simplify things. 

I think making it more generic and less custom is the safer bet.

Refinance and pay the downpayment.

Once your income is stabilized, you can do a refinance to remove your coborrower back off of the conventional loan. 

But as for the seller finance, would the loan to the seller be the difference between 450k and the refinance number of 220k?

If I had just bought this property and could force some appreciation, I could refinance and hopefully extract that equity within a year, for example--but since this house is paid off, refinancing would introduce a new mortgage payment.What are the options here?

If a cash out refinance, many lenders will allow the cash out to satisfy the reserves requirement.DSCR lenders generally let you vest either individually or as an LLC.

.• This balloon payment will be paid through a cash-out refinance of an investment property valued at $198,000.7.

Best bet though is a local community business bank.. 

You don't need to know everything to get started; you need a foundation to build on, and the rest will come through experience and then refining your education.You can build a basic understanding of investing in 3-6 months.