First off, welcome to the forum.
Second of all, THOSE BASTARDS !!!!
Honestly there are many on this site who have dealt with this type of aggregious violation of the single-family sanctity of the zoned residential area. First, determine if the use is a legal nonconforming use, legal use, or illegal use as set forth in the zoning regulations. If the use is illegal, pressure your elected officials to remedy the situation through aggressive enforcement. If the use is a legal nonconforming use, verify that the operation has followed the zoning ordinances nonconforming use provisions which typically limit expansion or intensification of the use. This may include expansions of structures housing the use or to outside activities, including the parking of vehicles.
Bottom line --- make the elected officials accountable. Attend a public hearing of the governing body (City Council, County Commission, Board of Alderman, etc.....) and say something about it during the "Public Comment" portion of the hearing. Elected officials absolutely love it when unexpected critical comments come from left field during the "Public Comment" part of the meeting. There's no better way to get action.