If this is your first car, I would think twice, unless it has recently underwent a MAJOR restoration.
My first car was a 1967 Pontiac Executive. It was well maintained and ran well when I bought it, but more gremlins shown up that you could imagine ( if you never have drove a 20+ year old car before). Panels that appared to be in good condition started rusting off, the car wouldn't start half the time due to quirky electrical systems, gauges wouldn't work... that's just half of it.
Gas mileage will be bad. I wouldn't think it would get into the 20s for highway, and town will be equally as bad. Old carburated engines were notoriously bad on gas, so don't it's better to be pessimistic with their mileage than optimistic.
You are best to take a mechanic or someone that knows ALOT about cars with you. If you can't , take a test drive straight to a mechanics place, and pay them to inspect it. You'll need to know just exactly what the problems are if you intend on driving this everyday.
If this is a secondary car, I say have fun with it. But as a primary first or second car...
unless you become a hell of a mechanic..