The buyer can arrange pre-qualification with a bank before they start looking for a house. This means the bank agrees that they to lend you up to a certain amount of money before you start looking, and that can make the buying process go a little faster. However, when you buy a house using a mortgage to finance it, you and the bank own the house together. Your share is the equity, and over time as you pay down the mortgage, your share of ownership becomes greater.
With regards to bank-owned property, does the bank own it as a result of a foreclosure? If they do, you will want to make sure you have an independent title exam run on it, because when you buy a home, you acquire any outstanding liens against it. This is why a title exam is run at the time of purchase. In general, the interest of the bank that is handling your financing and your interest is the same, because you own the property together. The bank that is handling your financing is going to want to assess the risk on securing a loan with that piece of property.
You have to deal with the listing agent, as that is who is representing the bank real estate holdings.