L.N.
Why not start getting him used to the idea? The trick will be to make it fun and not stressful for you or for him.
We started with our son by just taking him in to sit on the potty in the morning when we woke up. We would sit there with him or really early on, sometimes I would sit on the toilet also. Mostly we just wait a while, read some books, see if he had to go, play with a few toys etc. If after a while he didn't go either pee or poo then we would get up and move on. But usually, he would at least pee and often poop once he got in the habit.
We are still waiting for our 19 month old to get to the point where he can tell us that he needs to go and express an interest on his own to go to the potty but if we catch him "grunting" like he is making a poopie and we put him on the potty, often he will poop there.
It definitely saves on diapers and worrying about finding messes there! for the most part now we are just dealing with urine in the diapers.
Good luck!