As a Seller, the listing agent (the Realtor you hire to sell your home) charges a fee that is based on the sale price of the home. This can be 4% to 6% depending on the level of service you need.  Roughly 3/4 of all San Francisco homes are sold with a 5% commission.  The Realtor pays for all advertising and marketing associated with the sale. This fee also covers the fee for the co-op agent in the transaction (the agent that represents the Buyer). The Realtor's fee, or "commission", is paid out of the Seller's funds at closing so you don't pay unless and until the home sells and closes.  In San Francisco Seller's customarily pay the county transfer tax at close.  Generally it's $6.80 for every $1,000 of sale price but can vary based on the final sales price of your home.

The Seller's only upfront fees would be for repairs/painting/cleaning of the property before it goes on the market, or for professional staging.  There may also be some minor fees for required reports and forms including when your Condo association charges to make copies of your HOA documents.  Some Sellers will spend nothing for preparation, others will do complete remodel jobs in the tens of thousands in the hope of earning even more back on the sale.  Professional Staging can cost up to 1% of the sales price, but will often earn much more in return.

When the market is especially fast paced you may want to get professional inspections and provide the report results to all prospective buyers.  This reduces the chances the winning bidder will back out and/or allows you to sell your home "as-is".  Inspections range from $300 to $1000.  Your Realtor can help you decide whether or not your home is better off with or without pre-sale inspections.

As a Buyer, there is no fee for using a Buyer's Agent since the Seller of the home you purchase will be paying the Realtor fees. However, in addition to closing costs there are some minor costs associated with purchasing a home. After your offer has been accepted, you will go into the inspection period. This is when you hire a Home Inspector to carefully examine all aspects of the home and write a report of the findings. Items needing repair can be negotiated with the Seller if the Seller is willing. Most inspectors charge by the size of the home since larger homes will take more time to inspect. An interior Condo inspection is roughly $300 whereas a full inspection of a Single Family home is about $500, and can be $1,000 if you also get a Pest/Mold/Termite Inspection which is always recommended for older homes in moist areas like the Richmond and Sunset. Your Buyer's Agent will provide several recommendations of trusted professional for you to hire.  

Before the closing, you will need to purchase Homeowner's Insurance (Hazard Insurance).  This is similar to renters insurance and the cost will depend on the type of property and coverage you get.  Six months worth of your insurance premiums will often be placed in an "escrow" account at the closing. Your lender will pay this to the insurance company on your behalf out of this account.

There are also costs associated with applying for, and obtaining a loan, as well as Title insurance, appraisal fees, and other closing costs. A good rule of thumb for closing costs is 2% of the purchase price (this is only to be used as a guide. Please consult your lender for the actual costs).  These costs must be paid in cash (wire-transfer or cashier's check) at the closing table, unless your lender allows you to roll them into your financing.