There are different stages of a foreclosure, so it depends on what stage the property is in.
The earliest is after a Notice of Default. The homeowner still owns the home and can negotiate with the bank on a sale. If they are upside down, it's usually a short sale. Short sales can take months to get an approval on your offer because both the homeowner and the lender have to approve the sale. The financing for this stage would be the same as a regular sale, but the lender foreclosing may make their acceptance of the offer contingent on you being able to get your financing in a very short time period (we were asked to make it happen in two weeks).
The next stage is a public auction. If the home is at auction then the property is generally sold "as is" and for cash only. You must qualify with cash before you arrive at the auction.
The last stage is when the property is bank owned (aka REO). This sale is similar to a regular sale. The bank will have a Realtor selling the property. You should have your own Realtor too. The property is usually "as is" but you can get your financing the same as any regular sale.
Any way, I'm not a Realtor, I'm just a person that's been looking at foreclosures as a way to increase the possible homes I'm looking at. I've been through a short sale process for four months and in the end I did not get the house. The house is now up for auction and I'm trying to decide if it's worth trying to get cash together to buy it. It will be very difficult for me to do that.