The question above is one that I have heard dozens of times over the years. Some home buyers hear about the deal that their friend or relative got when they bought a home, and they're curious to see if this is the norm.
In a nutshell, there is no standard formula for real estate prices. Just as there is no "national" real estate market (markets are local), there is no set percentage that can be negotiated off of a listing price.
My answer to the question in the title is as follows:
"I wish I could tell you that you can get 3% off, or 5%, or any specific amount, but this is something that has to be evaluated on a case-by-case basis once you find some places that interest you. We'll have to see how long it's been on the market, whether or not and when they reduced it, stuff like that.
A home that needs some work might be easier to negotiate than one that's in perfect condition, or a place that's vacant might mean they're making two payments already.
Truthfully, I can give you a better answer once you've found a place that you want to pursue."
A little long-winded? Perhaps, but it's also the best answer that I can offer.
If you are a home buyer reading this post, I hope this comes in handy. If you're an agent, feel free to steal this answer for your own purposes. :-)
I'm not typically one to advocate memorizing scripts for various situations, since it's more natural to put things in your own words, but if you're new to the business, this gives you an outline to start from.
Thanks for reading!
Photo credit: http://www.flickr.com/photos/drachmann/327122302/