I am helping a small private bus service sell their retired mini buses. All the buses are first owner, maintained to NY DOT specs for school buses for their entire life. I am helping sell them because I really like working with the garage manager. I have bought two buses personally from him and others for friends. He is honest and straightforward about any flaws. If he doesn't like the mechanicals on any of his buses, they go to scrap or to a wholesaler.
I have left the sold buses posted as a reference for anyone shopping. Keep in mind this is different from an auction. You can talk to the mechanic who has worked on the bus and you can say 'no' if you don't like it when you see it in person.
My direct contact information is on the website, along with lots of other mini bus info. https://minibus4u.weebly.com/buses-for-sale.html