depending on the degree of the termite "problem" there are various things you can do...
a termite "problem" can mean many things..could simply mean there are termites in the ground near the house.
if there is structural damage due to termites....eeeek?
if there are termites present but not yet an infestation (or much damage) an exterminator can take care of the problem...the cost of wich should be taken care of by the seller.
so, either you or the realtor have to find out the degree of the "problem", speak to a reputable exterminator, negotiate with the seller in regard to the "problem" and how treatment of said "problem" will be payed for if the "problem" isn't so severe that you decline in purchasing the home.
