... So how would a wizard make make money in the modern world ...
Magically-insightful financial info would seem to be among the most-lucrative options.
Knowing how & where to invest -- and
not to invest -- looks like a winning strategy.
Harry seems to have a talent for "finding" -- I bet he could "find" all sorts of unclaimed valuables, in the right places. He could be a gold-miner, a treasure-hunter, etc.
If willing to break mortal law, wizards could smuggle amazingly well... veils (or simple illusions) to hide valuables, Ways through the nevernever to bypass customs entirely, etc.
Vigilante wizards could magically-spy on drug-lords, sleep them, and swipe a bunch of their cash.
But also, it's clear different wizards have different proclivities & talents. Some will likely be more-inclined to some pursuits than others. I presume not
every wizard has a relatively-easily-monetizable talent... but that
most do (if they aren't burdened by the kinds of ethical qualms Harry seems to be).