Whenever a sale is made, it involves a contract. Such a contract might include specific terms as to what the purchaser can do with what he has bought. (For instance, if you buy a disk containing computer software, the contract embodied in the licence usually states that you can only install the software on a single computer).
If you buy a betting tip from one of the firms which advertise in the racing press, there's probably some 'small print' which states that the information is for the use of the purchaser only and must not be passed on to third parties. To do so (with or without charging for the information) would be illegal. (This is comparable to lending a friend your disk with commercial computer software on it. It's illegal, whether or not he pays you).
However, if you buy a tip from a guy in a pub (if you're that gullible), and he doesn't insist that you don't pass it on, you're free to give or sell the information to anyone else.
Of course, if you buy a tip from someone who knows that a sporting event is 'fixed' and you use it to place a bet, or if you sell the information to others, you're into the murky waters of a criminal prosecution for 'conspiracy to defraud'.
Chris