To go into a tattoo parlour depends on the policies of the company who own it. However to have a tattoo depends on the laws of your country. In the majority of the western world, the minimum age to have a tattoo is 18. Which is the age that you are legally responsible for yourself.
There is no age limit ... someone could be 95 years old and have a tattoo. There may be a minimum age limit however, and that could vary from state to state. The tattoo parlor would have such information.
Florida law does not stipulate a minimum age if the minor has parental consent. However, most tattoo artist require a person under the age of 15-years to be accompanied by an adult in addition to having the required notarized statement of parental consent.