In order to buy life insurance on another person there must exist insurable interest between you and the person you want to insure.
Insurable interest basically means you rely on the other person for financial support, and/or you would stand to lose financially if the other person were to die.
Since you would be paying for your father's funeral, you do stand to lose financially upon the death of your father.
Insurable interest usually exists between spouses, parents and their children, siblings, relatives, and business partners.
You may be able to buy life insurance on your father; however, you will need his permission, his signature on the application, and he may need to answer some health questions, and possibly have to take a physical exam.
In addition, there are some life insurance plans that offer no exam life insurance.
But, if your father is ill, he may only qualify for guaranteed acceptance life insurance depending on his health, age, and the insurance company.