RE fees to consider if FSBO

Good afternoon,

I am looking at a FSBO. The seller says they are flexible on the price since they are avoiding RE fees. Are the fees just the 6% RE commission or are there other fees I could consider when making a counter offer. I wondered about offering 80% of asking price. First deal, close to home, B- Niche grade neighborhood. I'd be glad to hear some feedback from a more seasoned investor. Thank you. Aaron