The average cost of buying and selling a house in the United States can vary widely depending on a number of factors, including the location of the property, the condition of the property, and the real estate market conditions at the time of sale. Generally, the biggest expense associated with selling a house is the real estate agent commission, which is typically around 5-6% of the sale price. Other costs can include marketing expenses, closing costs, and any necessary repairs or renovations to get the property ready for sale. On the buying side, expenses can include the down payment, closing costs, and any fees associated with obtaining a mortgage. It's important to note that these costs can vary significantly from one transaction to the next, so it's important to work with a qualified real estate professional who can help you navigate the process and ensure that you get the best possible deal.