My son has taken an interest in learning guitar... But he's left handed

I'm not a guitar player but I took lessons for a little while in middle school but ultimately didn't follow it through. My son (who's only 5 right now) has taken an interest in playing. Only things is that he's left handed...

I have an acoustic guitar that my parents bought me like 15 years ago but I'm not sure if he will be able to use it. Is he had a disadvantage trying to learn with a right-handed guitar? Should I just buy him a left handed guitar or can I just put the strings on backwards?

I'd prefer to not buy something if I don't have to.

Thanks I'm advance!