The main thing you want to do is great pre-qualified by a loan officer. There are plenty to talk to on this website. Once you got that done you will know your price range and what is best for you. Pretty much every time (9.5 out of 10) you put an offer on a bank owned/reo you will need to submit a pre approval letter with your offer. That is about it inless you are inquiring about purchasing a home of some court house steps? Hope this helps you out. Best of luck and happy holidays!
Lending requirements are tougher for investors where they may require you to put more than 10% down. Some homes are also is such bad shape that no lender will give out a loan on them and they have to be purchased in cash.
As I said, every situation varies. If you have a buyer's agent representing you, he/she can walk you through it.