Buying A Property With A Relative

Hi, My wife's sister's husband and I are planning to buy a 1200 sq.ft land in Chennai and construct a house there. It'll have one 2 BHK house at ground floor and one at first floor. He'll stay at the ground floor and I'll rent out the first floor house. Please answer my following questions and note that these questions are only related to the deal between me and him not related to the land. Assume that the land is free of all legal issues. 1. Can i independently sell my share of the property when I want without his permission? 2. Legally, Does owning the ground floor house or first floor house matter? 3. What are the important statements or lines that we should have mentioned in the agreement so that any conflict in future can be easily resolved? 3. Should I have a separate lawyer to look into my side deal so that I'm not cheated (though I usually trust my relative)? 4. Any other points I need to watch out for? Thanks in advance.