As value is determined by what someone is willing to pay and the seller is willing to take, TRUE value is only determined at the sale. Anyone saying they know the answer is only making an educated(?) guess, or saying what they believe you want to hear.
Only work with a realtor that has a good reputation (use any search engine with the name of the realtor as a search criteria) Ask family/friends/co-workers, et cetera.
DO NOT SIGN an Exclusive Right To Represent. ( A buyer's agent is supposed to serve Your best interests, an Exclusive Right To Represent. serves the realtor's best interests, NOT yours)
Best of luck,
Rey Hollingsworth Falu
Licensed Associate Real Estate Broker