Calculate your monthly average expense then devided by the number of your family members. use the result as the estimated expense of each of your parents plus medical insurance. Double check your monthly net income (shown on your previous tax notice of assessment) to make sure your net income will sufficently cover the total expense when they are with you. If not enough, adjust the estimated expense (for example excluding their share of house expense). If they just visit you for one month, no problem on this whatever, either your income covers or they bring the amount here. But if you are sponsoring them for a long term, you have to check the miminum standard of living expense by Immigration Canada for each city in Canada.
Good luck!