In the United States, some casinos are owned by individuals, some casinos are owned by large corporations, some are owned by indian tribes.
no
21
Yes, there are casinos in which you can legally gamble at 18. It depends on the individual state laws. Almost all state controlled casinos require you to be 21 years old, Native American casinos...
There are casinos in just about every city in Nevada, from the smallest to the largest city.