You will need to pay a Realtor for a CMA or list with one. If you do not go that route you may just pony up $500 or so for an appraisal.
It costs Realtors money and takes time to arrive at a marketable sales price of a home. We usually dont just throw out numbers to people on the fly.
If you are looking to sell I suggest interviewing some listing agents and then obtain market value from them.