I have a client who has conducted business for almost 20 years in the same location, but the type of business does not conform to the use requirements of the local zoning code. He has not had any problems or complaints from anyone during that period and has developed considerable "brand identity" in this particular location, but he would like to know that the zoning situation will not cause a problem if he decides to sell the business. The use is not "grandfathered" as a legal nonconforming use because it was started after the zoning regulations were approved. As a general rule local officials will not enforce the zoning requirements unless a neighbor complains or the nonconforming landowner applies for a city land use permit. The business in this case is located approximately 200 feet from another zone where the use would be permitted, but because there is another business between my client's nonconforming use and the proper zone a zone change on the zoning map could be difficult to achieve. Here's the question: Is there any legal principle, perhaps akin to equitable estoppel or a statute of limitations, that would hold that city officials are prohibited from enforcing the zoning code or denying a city land-use permit based solely on the fact that the noncompliance has continued without objection for many, many years? Thanks.