There is no general rule of thumb as to how much you should offer on a house. Each has to be looked at on a case by case basis. If the property is priced at a point where it is a really good deal, it can sell for the full price or more!
In the end only you can decide how much you should offer. Beauty is in the eyes of the beholder and when buyers make offers it is the norm that their offers will vary based on their motivations, situation and amount of their desire to purchase the property. Usually, buyers look at many homes before they make a purchase and as they do they acquire the ability to be able to see which homes are good deals and which homes are overpriced. If you feel the home is overpriced, you would probably want to make a very low offer or just not buy the place. Conversely, if you love the home and feel it is a great deal, you may be willing to pay the full price or more.
If you are just starting out looking and do not have enough experience to determine how much you want to offer, you can always ask your agent for their opinion. Having said all that, without physically seeing a house, there is no way to make a fair determination of value. This is where the Zestimate comes in. Zestimates can be very high, very low or right on the mark. The reason for this is that the Zestimate does not take into consideration condition of the property and the desirability of any particular block (as you know here in Brooklyn the difference of a block or two can be very dramatic! Hence you cannot read to much into a Zestimate. At best it can guide you as to average market prices and at worst is can be completely way off the mark.
If I can be of further assistance, contact me direct. Good luck!
Mitchell S. Feldman
Associate Broker/ Director of Sales
Madison Estates & Properties, Inc.
Office: (718) 645-1665/ Cell: (917) 805-0783