Mortgage brokers, mortgage agents, and mortgage lending

I remember when we were thinking about selling our first house, we thought you could either use a realtor or sell it ourselves. Those were the only options. Option one meant we had to pay a commission and option two meant we did not have to pay a realtor. Of course we chose option two because the market in Colorado was pretty good at that time. Well, we had a couple of people come through but their finances were bad, after those few people came through we decided to use a realtor. Here is another option:  Auction your house?? I say that with a question because that is not an option I would have thought of. If you bought a house at an auction, how do you get a mortgage? Please share if you are a mortgage broker or banker that have taking care of funding for a house that was going to be purchased at an auction.