Investors have been known to purchase deeds all the time before the auction is held, and bring the mortgage current while they continue to market the property. Investors often opt to bring a mortgage current before they attempt to payoff the mortgage because most states have laws which allowed the registered owner at the time of deed transfer some recourse to claim the equity in the property at a later date, if it is proven they were defrauded. To avoid these claims investors simply bring the mortgage current. These laws cease to be relevant if at the time of deed transfer the property is not in foreclosure.
To review the foreclosure laws in your state you can click the link and select your state, http://www.worldclassmemberservices.com/ForeclosureLaws.html