pros and cons of buying a house for investment with mother in law and a spouse

My mother in law is willing to put the down payment while my partner and I will take a mortgage. We will rent 3 apartments (townhouse). My mother in law will get the rent of one apartment. With the rent from the second apartment we can pay our mortgage. And we can save paying rent by living in the third apartment. What are the pros and cons of each side? Is that a good investment for all parties?