It's possible he is trying to escape poor living conditions in Ghana, and rather than stay in Canada just for a vacation, he may try to stay indefinitely (illegally).
He could also try to apply for asylum once he is in Canada (if he was living in particularly poor conditions with human rights violations), or he could apply for an extension to his temporary resident visa (to give him time to sort out what he wants to do or where he wants to live), or finally he could try to immigrate to Canada and apply for permanent residency.
Canada has one of the most generous immigration policies in the world, although admittance is highly dependent on things like his current occupation, vocational skills, academic education and financial situation. Many Africans would do anything for the chance of being able to fly over and live in Canada as a free individual with access to our many social support programs and higher living standards, for many it is just a dream.
Note however that he will require a valid Passport and Temporary Resident Visa in order to enter Canada... Otherwise buying the ticket will be just a complete waste of money.
I don't really see how this could be a scam operation, unless if after you buy the ticket he decides not to pick-it-up and then claims that they wouldn't let him pick-it-up and then asks you if you can just wire the money over so that he can buy the ticket himself to make things easier. That would be a definite red-flag.
Also how long have you been talking to this person?
Also as Ashcan said, he could be using the name of someone who is actually planning on buying the ticket, rather than his own name. Also if the airline lets him change the name on the ticket (which I assume they won't let him do) then he could try to sell the ticket to the other person after the purchase.