on A, #1 position lien give you right to foreclosure the house

on A, #1 position lien give you right to foreclosure the house only when the home owner did not redeem and pay you back on time. depends on which state, this period can be between 1 to 5 years, you will earn your interest on this certificate which setforth by the state.

at the end of this period, if the home owner fail to pay you, then you can bring the house to foreclosure, ie sheriff sale/mortgage sale, by then you can payoff the second, third or what even lien the house had against it. by then, the procedure just like B.