There are a couple of techniques where you can profit without risk, such as silver mining or arbitrage, but generally speaking it is not as simple as people fondly imagine.
It’s very rare to find someone who understands the concept of fluctuation. The uninitiated never understand that a earlier professional gambler might lose for months on end, yet still profit overall. Usually this is mistaken for compulsive gambling behaviour.
People scoff when they hear about how even the most skilled card counters can theoretically have losing years.
Part of the confusion is due to an imaginary concept most of the gambling texts refer to called the “long run”. It is usually explained that a gambler who has the best of it will endure losing periods, but that overall he will end up ahead.
People then ask, how long is the long run? 1000 hands of blackjack, 100 sports bets, 5000 hands of poker?
In fact, this is just not how it works
There is no point at which the long run “kicks in”. What actually happens is this: When you make a series of bets with an advantage, you can win or lose. However, the longer the series of bets, the smaller the chance that you will be behind, in the same way that a sound becomes fainter and fainter. The chance of being behind never actually vanishes. Nevertheless, it does become so small that over a long enough period of play, it decreases to the chance of being struck by lightning, and eventually into the realms of monkeys composing complete works of Shakespeare by bashing randomly at typewriters.