There is no rule as to how much less than asking you can offer. Don't be afraid to offer 15-20% less than asking, especially if the property has been on the market for a bit of time and there are no other offers in sight. No matter what your agent says, he/she is obligated to present it to the seller. Remember that you are not going to go down on your offer, so start below what you think the seller will actually take and see what the response is. If you don't try you will never know. I recently successfully negotiated the purchase of my condo at 17% below asking. The conditions were right and the seller wanted out.