You shouldn’t, but you can.
Firstly, here is why you shouldn’t. Your grill will fill quickly with ashes. This may clog the nozzles of your burners. And, if you are like me and not prone to clean your BBQ after every use, the ashes can absorb moisture or, worse, get wet. This acidic mush will start eroding the bottom of your grill. This ain’t bad if you were trying to convince your spouse you needed a new grill anyway.
But if you have an old grill and the burners no longer work, you can certainly remove all the old components and refit your grill into a BBQ. Not ideal, but there are YouTube videos about this.
Why not head over to your WE LOVE FIRE local dealer instead? I am sure they have a charcoal BBQ that fits your budget. And, what’s best, they carry the latest in ‘hybrid’ BBQ, meaning it can burn both gas and charcoal. Or some gas models come standard with a charcoal and smoker tray.