Enquiry regarding legality of notarized document

Hello sir, My query is as follows : One of my friend wants to give me some amount of money to be invested in stock market on his behalf . We both will be sharing the profits derived from it, if any. What I want is to be on a safer side and make a legal document mentioning the amount given by him, purpose , time period , conditions etc. Though as we are very good friend he insists on a verbal agreement but I want something which could be accepted in court if any conflict arises. 1.Sir so do I have to to write this agreement only on a stamp paper ? If yes then kindly mention the amount of st