Every casino game has a vulnerability, even slots. Advantage play is not free money, it's a job. You need skills, a bank roll, and to put in a lot of hours in casinos.
If there was a legal way of achieving that kind of edge, casinos would know about it. That kind of gain is incredibly noticeable if you're watching the gambler, which the casino is absolutely doing.
>Every casino game has a vulnerability, even slots.
This is even more alarming. Slots aren't a skill-based game, they're RNG machines with a mean EV that's substantially lower than any other game in the casino. The only possible strategy that I can think of for slots (besides breaking into the machine and changing the RNG) is to hunt down slot machines that award an accumulative jackpot and play them when you calculate that the EV is positive. Even then, this is a rare circumstance and your gains would be small.
Good card players have lots of ways to gain advantages.
http://www.cardplayer.com/poker-news/25107-poker-legend-phil...
Point is, he's the most famous card player in the world playing at the highest stakes at a top tier casino.
There are plenty of low profile players who can do the things Phil knows how to do. Casino's have a hard time distinguishing a lucky run from an advantage player they haven't seen enough times to catch their attention. The last thing they want to do is ban a high roller, so advantage players get the benefit of the doubt.
To make it as an AP you need a big bank roll, a lot of discipline to learn the games, access to a community of APs, and a lot of time for traveling and gambling. It's a job.
In one of Kevin Mitnick's books—can't recall which one, maybe The Art Of Deception?—he interviews anonymous hackers about their exploits, and one of the chapters is about a group of 4 people who did just that. They bought used slot machines, reverse-engineered the RNG in the firmware, found it was vulnerable. They exploited it to win a few million dollars over many months/years and many casinos. They spread their winnings over time, and they stopped when they felt it was too risky to get caught by the casinos.
People do make money playing slots, but it's real work.