For Love or Money — Carolyn Keene

NANCY DISCOVERS THAT WHERE THERE'S A WILL, THERE'S A WAY.. .TO ATTEMPT MURDER
One of River Heights's richest and most respected citizens, Charles Pierce, has fallen in love.. .and fallen out with his family. He asked his beautiful and much younger housekeeper, Nila, to marry him, and his heirs fear getting cut out of his will. But Pierce now fears for Nila's life, and he asks Nancy to investigate the threat.
With all of Pierce's money at stake, there's no shortage of suspects -- including his very handsome son, Philip. And Nancy has to wonder whether Philip's interest in her stems from affection, greed, or both. Either way, he spells trouble, and Nancy knows one thing for sure: by taking on this case, she's inherited a house full of danger!