I'd like to clarify Charles Butterfield's answer for you a bit. When Mr. Butterfield refers to interest, there are two kinds of interest: interest earned on a note, such as mortgage interest that has to get paid off each month in order to avoid default and foreclosure; and ownership interest. When he states you are subject to the interest of the holder of the first mortgage, he means two things. You have to pay the accruing interest on the first mortgage to keep them from foreclosing on you, and the first mortgage has an ownership interest in the property by virtue of its lien on the property.
Before you bid at auction, you need to know if you are bidding on a first lien or "junior lien". A junior lien is one that was created after another lien. The first lien created is the "senior lien" all others are junior liens except tax liens, which are before all others regardless of date of creation. If you buy at auction and find you have bought out the interest of only the junior lien, then you have to work out something with the senior liens (usually by paying them off) in order to clear your title. You also have to do the same with tax liens. So, before you bid on a home at an auction, first find out whether you are buying a junior lien or the senior lien and whether the owner is subject to an IRS tax lien, property tax lien, or state tax lien.
There are realtors who are capable of doing this sort of search for you. You can also order a title search of a property for a fee. You should probably also hire a realtor to interpret the title report for you. You can perform a public records search on the property. A realtor can do that for you. A realtor can place the bid for you also. Generally speaking, this is not for amateurs. You would be well advised to hire a realtor to assist and guide you. The fundamental question you need to ask the realtor, is, "Would you bid on this property, and if so to how much, if you had the money and goals I have?"
I Hope this and my previous answers on your previous posts on auctions has helped. Feel free to give me a call anytime if you want professional help. My phone number is 408-639-0211.