Question
I have a money tree that recently is turning yellow.  What is causing this?

Answer
Hi Lee Ann
There are a couple of different plants that go by Money Tree Plant.  One is a "pathos" aka Devils Ivy, which is a very common vine type of a plant.  I am sure you see them everywhere-dark green leaves with yellow splashed through them.  They can either be a hanging vine or climbing from a pole.  If this is the Money Tree you are talking of, yellow leaves means Under watering.  Pathos is one of the few plants that turns yellow when under watered.  A pathos can tolerate low light and the soil likes to get slightly dry between waterings.  
One of the others plants known as a Money Tree is a Jade plant aka "Friendship Tree".  A jade is more of a shrub type of a plant and has small,oval light green leaves and are more of a succulent.  The jade likes to be root bound and will actually do well in a dry area.  The soil likes to get dry between waterings.  If they are over watered, the leaves will get squishy and fall off.
There is another plant that they are now calling a Money Tree; aka "Pachira".  This is an Asian type plant that looks a bit like the Umbrella Tree or Scheffelera-approx. 5 leaves to a bracket that are med. green in color.    Sometimes you will see their trunk braided.  I believe that these are really some type of a 'Ficus' but will not swear to it.  It is believed by the "Feng Shui" masters that these plants will bring good luck and fortune. They feel that each leaf is a symbol: Metal, Wood, Water, Fire, Earth.  These plants do the best in a diffused light and allow the soil to get a bit dry between waterings.  If your leaves are turning yellow, you may be over watering.  From what I have read, do not despair if the older leaves fall off, new ones will take their place.
If you do not feel that these are they plant you are talking about, I would be happy to look at a picture of yours.  Sometimes nurserys will sell plants that I like to call "Novelty Plants"  with names like "Money Tree" or "Coffee Plant" or "Loofah sponge Tree" just to get you to think you are buying something unique.  They are usually a type of an aralia.
Good luck and let me know if I can be of further help.

Leslie