On and after the date when a plan has been approved for the rehabilitation of an area by the local legislative body, no permit shall be issued for work or work done in the area which is not in accordance with the plan officially adopted and made effective by the local legislative body: Provided, however, That the local legislative body shall provide by ordinance that the zoning board of appeals, if the municipality has such a board, or if not, then a board of appeals created for the purpose, shall have the power on appeal filed with it by the owner of real property in the area to approve a minor deviation from the plan for the area in any case in which such board finds upon the evidence presented to it, that the application of the plan results in unnecessary hardship or practical difficulties and a minor deviation from the development plan is required by considerations of justice and equity. Before taking any such action, the board shall hold a public hearing thereon, at least 10 days’ notice of the time and place of which shall be given by public notice in a newspaper published or circulated generally in the municipality and by notice to all property owners within 200 feet of the property in question, such notice to be by mail addressed to the respective owners at the address given in the last assessment roll.