The $1,500 Maxine spends on the new apartment is the equivalent of over $30,000 in 2021. The $5,400 she racks up in IOUs would be the equivalent of almost $108,000 in 2021.
Joe and Maxine McCoy moved to 24 West 68th Street, an actual 10 unit residential building built in 1910. It's located a block from Central Park.
In the film, Marty is mentioned as having "fixed" the 1919 World Series. This is a direct reference to the real "Black Sox Scandal" where members of the Chicago White Sox were accused of taking money from New York City gangster Arnold Rothstein to purposely lose the 1919 World Series against the Cincinnati Reds - which they did, 5 games to 3.