Home Purchase Private Mortgage Insurance is an insurance that will protect the Mortgage Lender. The buyer will pay the premium. If you purchase a home and put 20% as a down payment, there is a 10% difference between the down payment and the Mortgage Loan. The lender wants a guarantee on that 10% in case of foreclosure. 
How much is PMI? For simplicity, here is a low ball example of how PMI words.
- Home Purchase: $175,000
- Loan amount $157,000
- Insurer charges an annual premium of 0.49 percent
- For an annual premium of $771.75
- 12 monthly payments of $64.31 per month .
Now just multiply this up to get a pretty accurate month premium amount.
Note: Be sure and contact your lender when you reach 80%, as they must cancel the insurance. If not at 80% by Federal law they must at cancel at 78%.