I'm going to kick an old man out of my house.
Why would you kick out the old man out of your house?
He's very disgusting, I can't stand him to be in my place when he drinks.
You agreed to let the man stay in your house, so it isn't proper for you to ask him to leave just because he has a habit of drinking. Stick to your agreement and honor your word.
I haven't changed my mind. I'm doing it because I don't want him to continue staying here.
Unfortunately, you've already agreed to let him live there. You can try to get him to stop drinking, but he might have a lease that allows him to stay as long as he pays for the accommodation.