What kind of business was Jacob Marley in?

Jacob Marley was Scrooge’s business partner in the counting house. 

Jacob Marley died seven years before the book began.  Before that, he was the closest thing that Scrooge had to a friend.  The two of them were partners in Scrooge’s current counting house, called Scrooge and Marley.  A counting house is like a bank.  Scrooge and Marley would lend money to people.

After Marley died, Scrooge did not change the name of the business.  He...

Jacob Marley was Scrooge’s business partner in the counting house. 

Jacob Marley died seven years before the book began.  Before that, he was the closest thing that Scrooge had to a friend.  The two of them were partners in Scrooge’s current counting house, called Scrooge and Marley.  A counting house is like a bank.  Scrooge and Marley would lend money to people.

After Marley died, Scrooge did not change the name of the business.  He did not even change the sign.

Scrooge never painted out Old Marley’s name. There it stood, years afterwards, above the warehouse door: Scrooge and Marley. The firm was known as Scrooge and Marley. Sometimes people new to the business called Scrooge Scrooge, and sometimes Marley, but he answered to both names. (Stave 1)

Although Scrooge seems entirely unsentimental, leaving Marley’s name up could be a small bit of grief sneaking in.  Scrooge is definitely happy to see Marley’s ghost when he shows up, once he gets over the shock.  Marley wants to help Scrooge out while he is still alive.  Now that he is a ghost he has some perspective and realizes that it is not all about money.

“ … I cannot rest, I cannot stay, I cannot linger anywhere. My spirit never walked beyond our counting-house—mark me!—in life my spirit never roved beyond the narrow limits of our money-changing hole; and weary journeys lie before me!” (Stave 1)

Marley arranges somehow for Scrooge to get a chance at reclamation.  He will be visited by ghosts who will show him his past, present, and future so he can come more quickly to the realization that Marley came to—while he is still alive.  Scrooge tells Marley that he was a good businessman.  Marley’s response is that mankind should have been his business.  He should have been more interested in helping people than making money off of them.