Within the districts established by this Ordinance or subsequent amendments, there exist lots, structures, and uses which were lawful before the Ordinance was passed or amended but which would be prohibited under the terms of this Ordinance or future amendments. It is the intent of this Ordinance to permit these non-conformities to continue until they are removed voluntarily. The legitimate interest of those who lawfully established these non-conformities are herein recognized by providing for their continuance, subject to regulations limiting their completion, restoration, reconstruction, extension, and substitution.