Just out of curiosity, how did you come up with your offer price? Is the building damaged by fire or flood? Are there major issues with the property that you have knowledge of? Have you already discussed that offer price with the listing agent? There may be something I am missing here too so take this with a grain of salt.
I agree with what has been said, they want to know how serious of a buyer you are, and how far ahead you have thought. You may be able to secure a property with serious intent, but that is a seriously low offer. I am not saying it isn't possible for you to secure it, just want to play devils advocate for a moment.
Put yourself in the sellers shoes for a moment though, if you were the seller (I know this is a REO, but I have done many REO deals and believe me, the notion that they just want to "get it off their books" has not been my recent experience, especially recently), if someone came to you with an offer for $180K when you were asking $300K, would you not think: "wow I could prob drop my price on the mls to $250K and see what happens." Not saying it wouldn't happen, just if they have an agent already they are probably going to advise the seller to do something like this vs take an offer that low. I hate to be such a downer, but that agent has a fiduciary responsibility to that seller, even if it is REO.