House of Lust (1985)

Greedy businessman, Nelson Broadhurst, awaits the return of his 21-year-old son and heir, Ronny, from Harvard Business School to take over the family firm, Broadhurst Industries. Nelson's two daughters, Debbie and her sister, and Nelson's new wife, Dee, fear they'll lose their privileges when the kid takes over. They indulge in sex with the staff and each other while waiting. Nelson first has sex with Dee, and later with their maid, Tina. Dee has sex with her personal confidant and chauffeur, Charles. Debbie and her lusty sister have sex with each other, and then Debbie has sex with the handyman by the pool while her sister has sex with her masseur and lover, Bob. She warns Bob that she once had an affair with Ronny, who is her half-brother, and fears that it will be expected of her to leave Bob and return to Ronny when he takes over. However, once Ronny arrives, he turns out not to exactly be what they expected.