What Are the Monthly Expenses That Would Be Added to My Monthly Mortgage?

mortgage

1)I am plotting to buy a new home for the first time . What expenses(payment) would be added to my home mortgage like home insurance, mortgage insurance etc?
2)How can I lower my monthly mortgage? Some of my friends told that I have to pay at least 20% down payment rather than paying those amount after one year or so to lower monthly mortgage .
Thanking in advance.