Madelyn, Floyd's pen pal, has been sending her letters to "Floyd Lawson Enterprises" at his barber shop address. However, when Madelyn arrives in Mayberry she drives up to the mansion that Floyd's using in the charade. She would not know to go to that address because she's driving down from Baltimore and only knows the barber shop address.
In "Quiet Sam" (s1e39), Floyd mentioned his wife, Mabel, and her walking stick. In "The Jinx" (s2e17), Floyd mentioned his son missing a fly ball during a baseball game, yet here he is single with no children. Floyd did mention that he is a widower, so it's assumed Mabel passed away.
There's a continuity error with respect to Floyd's backstory. In "Those Gossipin' Men" (s1e15), Floyd takes his son to audition for a traveling salesman, believing him to be a talent scout for a New York-based television show. Here, it appears that Floyd is single with no children, otherwise, Andy wouldn't need to pose as Floyd's son. The reason Andy posed as Floyd's son is because Floyd panicked when Mrs. Grayson asked who Andy was. Floyd panicked and said "he's my son.".