Ballpark appraisal adjustment for non finished basement

[Michael Donatucci]

Working on a 1200 SF 3 bed 1 bath rehab for buy and hold. There are a lot of similar sized 3 bed with 2 bath comps in the area selling for around $270K, but not any 3/1s - most flippers are finishing basement and adding second bath. I don't think the return will be there to finish basement and add bath since it's a rental - I'm curious to know what I can expect from appraisers as a valuation adjustment for not having the finished basement with bathroom. Any thoughts appreciated!