All in all, there are free slots that pay real money, but you will have to be playing at real money online casinos as opposed to social casinos on slot apps, or playing titles in demo mode.
The number 7 has been traditionally associated with good luck and fortune in many cultures, and this belief has carried over into slot machines. In many slot machine games, the number 7 is often used as a symbol of luck and is featured prominently on the reels.