Continuation. Any use, any building or other structure, or any lot, which existed lawfully (including by variance), on the effective date of this chapter or any amendment thereto, and which fails to conform to one or more of the provisions of this chapter or such amendment thereto may be continued, subject to the provisions and limitations hereinafter specified. Any business owner or tenant may continue to operate an existing business, or any business in the same use category as the existing business, in a zone where it is not permitted by this chapter, and may sell or transfer it to another owner or tenant who shall be permitted to operate the same business, or any business in the same use category as the existing business, in the future.