You are asking a very common question. I feel that there is no correct answer to this question. If a house is "worth" $500,000, and it is listed for $700,000 then I would as a buyers broker of course suggest making an offer inline with the $500,000 "value". On the other hand I have represented buyers in todays market who I have suggested making full price offers on homes that were in my opinion under valued, and I thought in time would sell for above asking. You also should consider what the home is worth to you. I am making the assumption that you are going to live in the house. If the house has a brand new kitchen with beautiful green granite countertops, and you hate green, then this does not add value for you. You can search on http://www.Northportluxuryhomes.com to try and get comfortable with home prices in the area. Also I would look on Trulia.com for recent sales, and neighborhood sales trends. Use the following link: http://www.trulia.com/real_estate/Northport-New_York/