Old door lock tumblers can be easy. I have about 15 old keys from GMT400's. Half of them will open either door on my Tahoe but only the right one will start it. SWMBO's son locked himself out of his truck once and had ignored my advice to use a Hide-a-Key. Same thing, I took my handful of old keys and opened the door on the third one.
Screw a locksmith, save those old keys, you never know when one might come in handy.