In a seller's market, there are more buyers than there are homes on the market for sale, so most of the homes listed on the market will sell fairly quickly. Usually there is less than four to six months of inventory on the market.
In a seller's market, you are probably competing with a number of other buyers for the same home. It is not uncommon to find that the seller is considering his options while reviewing a number of different offers that are not your own. Sellers are not inclined to pay for anything that they don't have to, so you will have difficulties convincing them to pay any of your closing costs. Sellers wont wait for you to sell your home if there is someone else making an offer to close the deal sooner. Basically, the competition is fierce among buyers in the seller's market, and it is tough for buyers to negotiate a great price when there are several other buyers vying for a limited supply of homes.