The reason why many people choose to work with a knowledgeable realtor is to help negotiate and get the property under contract.
Another way to look at the home buying experience, is to ask yourself - at what price will the seller agree to sell his or her property to me?
Zero would be the lowest possible offer, but it wouldn't be successful. Finding the right strategy for an offer depends on a lot of different circumstances. How motivated is the seller? How many other similar homes are on the market? How long has it been on the market? Have they had any price drops? Are others offering on the home?
These are just a few questions that must be at least asked before you can make a successful offer on any house. Now, if you say, "I have $X.00 available and it's less than this. I can't spend any more." you can always find an agent to just make the offer and find out.
No one here knows the answers to the questions I asked or what the seller may accept. Find a great local agent to help you get the answers necessary and see what you can do.