The E2 investor visa is an avenue used by individuals who want to retire in the US. It is not easy to retire in the US if you do not have a close family relative who can sponsor you for your green card (the immigrant visa). Even this process takes a lot of time as it is subject to country specific processing times. However individuals who are desirous of retiring in the US, sometimes try to buy a US based business under the E2 visa category. However this visa requires stringent conditions which have to be met before it can be issued and there are always chances that the visa could be denied. Moreover this also has to be renewed periodically.
Actually the USA currently doesn’t have a visa which is specifically meant for retirees though many Europeans chose to spend six months (usually from November to April) in the USA in warm places like Florida on a B2 visitor visa.