I paid both sides of closing costs. 100% seller finance, 5% interest, amortized over 23 years, with a balloon payment of the principle balance due after 30 months.

My partner and I decided not to over complicate things with this method.

I put my criteria clearly in the listing: 3x income over rent, 85% on-time payment history on credit report, and good references from past landlord.The biggest mistake you can make is taking the word of a current landlord.

@Lukas Loveland We do monthly payments as well.

For one of my multi-family properties, I chose to dig my toes in the sand and make extra payments on the principal until it was paid off. 

So make sure your uses of the refinance money conform to business  purposew if you want to write off the interest.This method is commonly used in a 1031 consolidation exchange. 

Or, should I just take a fraction of money and put that towards a down payment and finance the rest with a 30 yr mortgage?

They are however good at 20-25% down commercial portfolio loans if you need a creative solution so it depends on what your intended use is, your preference is, are you trying to get maximum leverage aka lowest down payment or is rate or cost your main preference? 

We all have our own methods, and that is what makes us all unique.  

I think your biggest concern would be the pre-payment penalty that comes with most DSCR loans.