Apartment 713 by Kevin Sylvester

Secret ballrooms, hidden artwork and unlikely friends-welcome to the Regency, where even time moves in surprising ways!
Jake Simmons hates his new home.
The Regency is nothing more than floor after floor of peeling wallpaper and faded glory. Jake misses his old life. He misses the time when his mother was employed. He misses living in a house where the wind doesn't make the windows whistle.
Loneliness (and a trail of kittens) leads Jake to the apartment of an elderly lady, then to the bowels of the building and then to a part-time job assisting Danny the custodian. With each passing day, the building reveals more of its mysteries to Jake. The occupants grow on him too.
Unfortunately, Jake's feeling of belonging is short-lived: the city plans to demolish the Regency. Jake feels powerless. And then fate throws him a curveball. He's summoned to apartment 713. An apartment he's been told is off-limits. But when he opens the door . . . he travels to the past!
Alongside Beth, his new friend and guide, Jake begins searching for any clue that might help him save the Regency. As their friendship blooms, the mystery around the building's makers deepens. The Regency's own storied past will give Jake the key to saving his own future-if only he knows where to look.