call a Real Estate agent in the area where the home is located.
Harold Sharpe - Broker
So Cal Homes Realty
California Department of Real Estate Broker License # 01312992
All you have to do is ask a Realtor and many are willing to do a CMA for free. In a growing number of states BPOs cannot be done for a fee legally, and be careful as to why you want a BPO instead of a CMA.
You need to call a realtor in your area and let them know you are thinking of selling your house and would like to know what it is worth. We in the realtor business call it a CMA. When I do a price for lenders they call it a BPO (brokers price opinion).
Hope that helps