Occupation certificate Chandigarh

I want to sell an individual floor of a 3 storey house in Chandigarh. I own 50% share and I have already sold 30% and 20% shares related to the first and the second floor of the house in 2005. Now I want to sell my share i.e. ground floor of the house. I have a couple of questions about it: 1. The house is around 50 years old and the occupation certificate was not obtained after it was built. I have heard that in order to sell the house (my share), occupation certificate is not required, however after the buyer gets the sale deed registered, he/she will receive a notice from the Estate Office Chandigarh that the occupation certificate must be obtained within 90 days. I want to confirm if this information is correct. If it is, what are my obligations? 2. I have heard that if the buyer wants to finance the property that I'm selling, then he must get an MOU signed with the other co-owners of the house, otherwise the banks will not finance the property. Is this correct? The other co-owners are not interested in signing an MOU. What is the possible solution to this problem. Thank you.