"Professional Hunter" could mean two things: he is paid to kill, or he is paid to hunt. There are a lot more jobs guiding other hunters to make their special kill than there are getting paid to do the killing. People spend the big BUCKS for access to private land where I live (Colorado), and there are many outfitters who are looking for guides every year. Once you guide for someone who has a sucessfull hunt, they will very likely want you to guide them again, and will tip as well.
So, either have someone tape your hunts and try to get sponsored, or obtain access to private land and start an outfitting company, or work for an established outfitter and gain a clientele base. If you are making money doing it, you are a pro. Good luck!
I have worked for several outfitters.