I was browsing the Wyoming inquiries and saw your question. As a sales associate for a developer, I'm limited to selling only my neighborhood and can't sell your niece's home, however I wanted to share my experience. In general, Cody is increasing in price and the tourism season will be a good time to sell. As for seeing home sale prices, you need a professional Realtor like Johnny mentioned in another answer. Another option would be to hire an appraiser and ask them to come up with your current market value. A good agent will come very close to that same amount too. A big advantage to an agent is they handle everything and can keep a good 'poker face' during the negotiations - resulting in more money to you. Homes that are sold with an agent sell for well-over the commission amount when compared to those that sold by owner. You can look up the actual stats on Realtor.com as done by NAR. Also, putting up a For Sale sign in our yard is like saying "I need help selling my house - please, every Realtor in the area call me!" Eventually you will hire an agent, but the word will be out that you tried to sell it on your own and couldn't - making people wonder what's wrong with it. In a little town like Cody, don't stigmatize the house like this. Hire a professional from the start, who has pride in the product that you are selling, and will work as a true advocate for your niece. As I stated early on, I can't price the home due to my contract, but can certainly send you to one with a great record of selling.
Hope this helps! Rebecca