What is mortgage prequalification, and is it mandatory?

Source: Business Insider — 

Do you think you’ll be ready to buy a home soon? Then you may want to apply for mortgage prequalification with a lender. The process is quick and free, and you can usually apply online.

What is mortgage prequalification?

Mortgage prequalification is one of the first steps in the homebuying process. When you apply for prequalification, you give a lender your financial information, such as your credit score and income. Then the lender gives you an estimate of how much it may lend to you, which types of mortgages you’re eligible for, and what interest rate you could pay.