When is it too late to buy a home before it goes to auction?

First off, I'm in Texas.  I am not all clear on the foreclosure timeline for trustee sales that are to be auctioned on the courthouse steps.  If I was in contact with the homeowner who has already had a notice filed, and the auction date set, would I be able to purchase the house directly from the homeowner or is it too late?  Or, Would I have to buy it at the courthouse auction? If I pay cash, could I payoff whatever payments and penalties were due and close a deal before it even goes to auction?  

Bear with me, I'm new!