As a professional gambler my entire adult life, DON'T do it! I wouldn't advise anybody to follow the path I chose.
Why is that?
I never gambled full-time to finance my life, but only gambled as a 2nd source of income. So I might underestimate the toll a downswing might take on you, if that's the only source of income for you.
But at least from the outside it seems like if he had what it takes to succeed and he could handle the up's and down's of betting and the missing social interaction of a "normal" everyday job, that gambling for a living isn't a worse job than most others,
Ok, you lack the social side of a normal job (interacting with co-workers, being accepted/getting a certain standing because of your socially accepted line of work) and "security" of a regular paycheck (ok, that security can be faster gone than one thinks, esp. in todays economic climate), but on the upside you can earn a solid salary if you are good at sportsbetting, you can manage your own working schedule and don't have to depend on anybody.