Hi Brian; Your lucky to live somewhere that black locust is cheap!
Yes; You can definitely use locust as
fence posts. In my opinion they are among the best!
When you end up with a hundred year post versus the 7 - 10 year treated round posts. Who cares if it isn't "pretty"!
I am attempting to grow them here but I'm afraid at my age ,I waited to long. I wish I had planted 20 years ago!