On second thought, I'm in agreement with others who have suggested that there's usually a setback on all sides of a residential lot, usually 20 feet for a rear yard setback, in which no building or structure other than a fence can be constructed. Unless this fellow got an area variance from the zoning board of appeals, he would have to comply with setbacks and usually (1) he'd have to have a good reason why such setbacks would be waived, (2) the board would consider the adverse effect on neighbors and the neighborhood, and (3) most importantly, you and any other adjoining properties within (usually) a few hundred feet of any part of the neighbor's lot would have received a letter from the zoning board before their hearing and decision giving you prior notice of the request and a chance to view the application and plans on file at the planning department. Then you would have showed up at the hearing raising holy hell and if the board somehow ignored your complaints, you could seek review of the ZBA's decision in court within a short time window prior to the time of the structure or building's construction.