Some friends of mine had a rabbit as a house pet, and yes he was housetrained. He would use a litter box like a cat. They started litter box training him when he was a couple months old right after they got him, so I am guessing that 7 Months old would be a bit late to teach.
The only problem they had with him, and they soon remidied that, was the man of the house was retired, his wife still worked was in and out all day. The rabbit got really possesive of him, would hop up on his lap to be held & watch tv. lol ~ He would Pee on Everetts lap, we figured it out he was "marking" HIS PROPERTY! To remedy that they got a bunch of thick cloth diapers or burp rags, he would put on in his lap when he sat down and knew the rabbit would soon follow. Sure a good thing that rabbit pee doesn't stink like cat urine! 
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