Since these costs vary depending on both the location and what other sellers are offering to buyers in your neighborhood, I can't tell you exactly what that number will be. But here's a general rundown on costs:
As a seller, you're responsible for paying certain set costs, such as a grantor's tax (which in Virginia is $1 for every $1,000 of fair market value, based on the higher of assessed or sales value). You will also have to pay any homeowners' association fees and real estate taxes due, prorated to the closing date, as well as any outstanding utility, water and sewer bills.
You'll also have costs that can be negotiated, at least somewhat. These include settlement company charges, any fees your lender may charge for paying off the loan, and of course, the broker's commission.
For all of the above, as a rule of thumb, you can expect closing costs will be about 1.5% of the purchase price, and broker fees to run between 3% (if you use a flat-fee broker) and 6% (if you use a full-service broker). All of these costs are spelled out in the HUD-1 form
But since it's still a buyer's market, it's not unusual for purchasers to ask for help with their own closing costs, or to buy down the interest rate on their loans (their lender must approve this). If the buyers are unhappy with some aspect of the house, such as stained carpeting or old appliances, they may also ask for a decorator's allowance. For this reason, I don't think it's shocking to be asked for $7,500 in concessions.
The buyers' requests will be spelled out in the offer, and you don't have to accept them. However, if other buyers are doing so, you should consider doing it too. Your agent can find out the dollar amount of seller concessions for recently sold homes comparable to yours.
Regardless of what sort of deal you and the buyer work out when you accept their offer, you should also put a few thousand dollars aside for problems that may be revealed after the buyer has the home inspected—even if you have had your own home inspection done before you put your home on the market. You don't want your sale scuttled because of some loose flashing or a sagging porch. It's also wise to offer a one-year home warranty, which costs around $300. That way, the buyer will be calling the warranty company, and not you, should the washer break a month after closing.
And remember that many concessions may be worth making if the buyer offers you a good enough price. It's the bottom line that counts.