Is it correct to say "people having money" instead of "people who have money"? I.e. is it OK to use "having" as the opposite to "without"? In my opinion it is OK but a colleague of mine believes that it is wrong to use "have"+ing.
In terms of antonyms, "with" and "without" permit parallelism. "People with money _ whereas people without money _."
But you can create parallelism in other ways.
"People who have money _ whereas people who don't [have money] _."
I believe that "People having money" is grammatically correct, but it does sound a little odd to me. I cannot articulate a reason for my feeling that way, but, as a matter of personal style, I'd probably go with "who have."