Can a 17 year old have his own auto insurance in georgia?

No. An insurance policy is a kind of contract, and a contract cannot be enforced against a minor. An insurance company would be foolish to issue a policy whose conditions could not be enforced.

When my son was old enough to drive solo and have his own car at age 18, the cost of auto insurance was about $290.00 per month. That figure may be lower or higher than other parts of the country.

Certainly contact some agents in your area or on line.

yes. if he's licensed then he can ride it on the street, if he's not licensed he can ride it on private property.

No, they are not old enough to sign a contract such as an insurance policy. They will require an adult to obtain the policy for them.