To go into purchasing a home.. for you to ask.. how much to take off the price assumes that the house is overpriced and you should take money off.
Get comps in the area and make an educated offer compared to other homes sold in the area... maybe it is priced right. I recently listed and sold a home in one day. how? the owner said .. price the house to sell in 1 day, lets take all in to consideration and sell it quickly. We had three offers within 1 day.. two people came in 25k under asking price with all of these explanations as to why..and we told them no.
One person did their homework and Paid full price stating that even at full price, it was a great buy.
Don't go in thinking how much you can take off the price, educate yourself on sales in the area and make an educated decision.