Worthless but interesting information. The street address (10086 Sunset Boulevard) used in both the movie and the musical shares the same intersection of the mansion that Michael Jackson died in! (100 North Carolwood Drive Los Angeles, California)
The real mansion used for the 1950 film was located just 10 blocks south of Paramount Studios -- no where near the actual Sunset Boulevard. Director Billy Wilder considered the mansion perfect for his film but it didn't include a swimming pool, so the production constructed one. However, the pool was for 'show' only. It was not capable of operating as a functioning swimming pool. This mansion (and empty faux swimming pool) were used again in 1955 for Nicholas Ray's REBEL WITHOUT A CAUSE.