1. An insurable interest in the person.
2. The person's permission.
3. The person may need to answer some health questions, and take a physical exam.
There does exist insurable interest between a parent and child, which basically means you may stand to lose financially if the insured person, your mom, were to pass away.
Next, you would want to speak with your mom and ask her if should would agree with you buying a life insurance policy on her.
Then, you can either contact a local, licensed independent life insurance agent, or visit a life insurance website to learn more about life insurance and compare life insurance rates and plans.
Here's how you can learn how to buy life insurance online without any medical examination.