I saw this movie when I was about 8 years old (so in the early '80s). I did not hear much of the movie since I snuck into the living room and was secretly watching behind the couch when my babysitter and her boyfriend were watching it, so please bear with me. This movie is from the late '70s or early '80s.
There was this young boy (maybe 15 or 16) who was left alone in his mansion while his father was gone. There was a French maid (I do not know if she was French, but she wore the typical "French maid" attire) who appeared to be seducing him and I just remember that they pretty much just had sex throughout the movie.
Thinking back, I cannot remember any actors in the movie. I do remember that he had a friend who was pudgy and had a hot sister.
Pretty sure it is an American film. It was your basic '80s skin flick.