Why are you concerned about asbestos exterior siding? Educate & inform your clients so they can make up their own minds. Obviously its a old home, its gonna have old “stuff”.
I had a client ask me about the siding on the home he was buying,… “Do you think thats asbestos?” He asked. I said, probability is pretty good. He got this worried look on his face until I said. “Yup, probably one of the best sidings that were ever produced in terms of durability” He looked at me stunned. and I continued. "Mind you I wouldn’t chew on it, cut it or do any demolition without proper personal protective equipment if you had any of that in mind. If its left in place, and its still in good condition, its fine. As long as you know its potentially there.