Most professional gamblers, be it sports betting or otherwise, are not just going to teach you their trade if there's nothing for them to gain. Think about it: If every professional sports bettor pooled their knowledge and made the same bets, the odds would change and none of them would make money. It's in their best interest to keep their knowledge to themselves or sell it. All you can do if you'd like to learn to make the proper picks yourself is learn everything you can about methodology from the printed material available (never trust online crap) , and study the games and teams you want to bet on thoroughly so you can make informed decisions.
BTW, most of the people who claim to be professional sports bettors online are full of crap. Their looking to sell you something, or make money off you clicking on affiliates. I know of only one legitimate professional sports better online: Wayne Alyn Root.