Amatuer or pro, is there really a definition?

How do you classify?

Some suggest if 50% or more of your income is generated by photography, then you are a pro. I don't agree. Scenario, a homeless guy pics up a polaroid camera he finds on the street, takes a picture of a passerby and asks for $2 for the photo and gets it. He has no other income, eats in soup kitchens and lives in a shelter......is he a pro?

My situation, I am a licenced builder and earn good money from that. I also work for different sporting groups and manufacturers as a photographer. The money I earn from my photography more than pays for my gear and I am preferred over other photographers by the groups of people that use my services. I am not cheap, I charge the same day rate as I do for building homes. Both of my businesses are registered with all of the governing bodies. It depends on which business I am spending more time at as to which generates more income.

I do not consider myself a pro because I think the term implies a bit of conceitedness. I just enjoy photography and capturing the moment for myself, or capturing the image for my clients needs.
I am curious to hear what you guys think defines a pro.
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Warm regards, Dave.