Hi,
a good saying to remember when "bartering" is " if your first offer does not embarrass you, it is not low enough".
When buying our house my first offer was $60,000 less than the advertised price, the price was just more than the house you are looking at. We ended up $45,000 less than asking. Some people are desperate to sell and some are not, we were in a good position, had six months to run on a rental,nwhich wasn't expensive, but we were happy to stay there if things didn't work out.
You can always up your offer but not very often will you get away with dropping your offer.
Good luck.