Owner finance or not. If owner finance (advice welcome)

[Elvis Nasi]

I am walking a 4 unit apartment building next week. I can qualify for a bank loan (local CU) with current offerings (15% down; 20y amortization; 6.5% interest). The other option is owner finance (owner is open to it).

Purchase price (what I am thinking based on area and other properties) = ~$335k

Monthly rents = 4150$ 

Taxes = $9570

Insurance = $1950

Water & Sewer = $925

Should I finance via bank. If owner finance is an option, what can be a good offer? Thank you.