Why should I use a broker to purchase an aparment???

I am interested in purchasing an apartment in a specific building in Manhattan. I am using a broker for this and we are planning to make offers. First, I asked him what our first offer would be. He told me to make the first offer at 10% below asking price. When I did my research myself, the price per square foot (based on transactions that closed in the last 6 months) is justifying an offer that... [more]

I am interested in purchasing an apartment in a specific building in Manhattan. I am using a broker for this and we are planning to make offers. First, I asked him what our first offer would be. He told me to make the first offer at 10% below asking price. When I did my research myself, the price per square foot (based on transactions that closed in the last 6 months) is justifying an offer that is 20% below asking price!! Why is my broker not telling me this, why do I have to do the research and why is he proposing an offer only 10% below asking price? Are brokers that assist buyers not supposed to provide me with information and help me get the latest price? I am starting to wonder that brokers (at buyers side) are just trying to close deals so they can get the commission? (so they don't really care about the client trying to get a low price)? [less]