Buying out a silent partner on a mortgage?

About 3 years ago I found a vacation house in upstate NY selling price of $106,000. I have a friend who works for my family want to go halves with me. Previously he went bankrupt and could not get his name on the mortgage. So I'm on the mortgage by myself, everything is in my name, except we have a joint checking which is used for all the bills (mortgage, electric, TV,) And we split everything 50/50. He currently bought property up by this house and plans on building his own and he wants his half boughten out. And wants to just rent his room for another 1 or 2 years. We have not talked any terms yet and I don't feel the need to get lawyers involved yet. I'm planning on just going off the purchase price of $106k, unless he wants an appraisal and give him his half of what's paid off on the mortgage and whatever the closing costs were, I shouldn't have to pay him back the interest or electric bills right? I want to be fair cause I'm still see him everyday and I also don't want to pay more than I should.

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