Post office MIS is not a regular investment scheme. You can only invest money in multiples of ₹1000.
If you are investing smaller amounts (like less than ₹10,000), the monthly income would also be very small. Therefore, this scheme is better for those who have collected huge amounts of money so that their monthly returns are also higher.
Keep some amount of your savings in your savings bank account for emergencies. Don’t put all your savings into post office MIS because the monthly income from this investment would be very low and might not be adequate during emergencies.