Will on a plain paper is a legal document

Greetings, My in-laws have 2 daughters, after selling their hi-locality house they purchased 2 builder floors in my mother-in-law’s name. They handover one house to me for living and in another they were living. Later my father-in-law expired, and 1 year ago my mother-in-law developed cancer. The house which my in-laws were occupying has transferred to her elder daughter through register deed. But our home is still in my mother-in-law’s name as I am not having money to pay for registration deed. To avoid future adversaries, I thought to get a WILL made from her in favour of my wife. Que1) The WILL with computer printout on good quality plain paper duly signed by my mother-in-law and 2 witnesses, is best option for future transfer of ownership through registration deed. 2) Can my sister-in-law and her husband can be the witnesses. 3) I researched online and found that a WILL made at home and registered has the same legal value. 4) What future obstacles may arise.