Is there a limit of how much life insurance a person can buy on himself?

Yes, but that limit depends on the underwriters at the company where you're buying the policy. Attempting to purchase an amount of insurance that doesn't match your income or obligations would tend to raise eyebrows in an underwriting department. (10 times your income is probably okay, 100 times your income is probably excessive) If there is a valid reason for the amount of insurance that you want to purchase, you probably won't have any problems.