Pa seems to not license bounty hunters at all; same with Hawaii, which is how a convicted murderer (Duane Chapman, aka Dog) is one. No firearms, no taser or other stun device, no armor except while working and with a written declaration from your employer that you need it for your job (shouldn't be hard to get). And you can't do it unless you get hired by someone (or if you become a bail bondsman yourself, but then your main job is paperwork), and you might have a hard time getting hired ( Chapman was hired by his wife, avoiding these issues) but there's no reason it's inherently impossible.
Now, if your friend wants to do by his because he thinks it's like being a cop, that's a very bad idea -- there are massive differences between the jobs (e.g. Bounty hunters don't have nearly as much protection against a lawsuit as police officers), and if your friend acts as though he is a cop, he'll go to jail. Period.