I believe that the Excel Group should have sent you to the Access Group.  It
is really more of a database application and one thing that you did not
mention was the ability to credit payments so that there would be some way
of coming up with a balance owed or not.

I think I could probably do this in Word, but it would be easier in Access.
Note that I said "easier" NOT "easy"

There maybe some low-end accounting software that would be easier than
Access as a lot of the functionality that you need would likely be built in
to it.

Take a look on some of the "Shareware" sites and see what you can find.