I've been looking into it and there are no current restrictions on licensing or anything like that. The topic Squelchtone linked has some information regarding the HICPA which to my understanding does not apply statewide.
My understanding leads me to believe that you are permitted to offer locksmithing services for a fee with a valid business license. That means you could register as a sole proprietor LLC, if you're a one-man operation.
Also, it's good to see another person from PA here!
