You need to specify a neighborhood, the number of BR, BA, whether 1 story or 2, features, amenities and upgrades. Then what will you do with the info? Do you have a negotiating strategy beyond just your price offer? Do you know what you need form the seller before you make an offer? What about the option period? Are you dealing with a FSBO or an agent for the listing brokerage--neither has any motivation to serve your interests and advise you. For that matter, an agent for a listing broker will want to get as high a price as possible from you.
Buying a home is unlike any other purchase, and requires a great deal of knowledge and understanding in a range of factual matters and processes. Since using a buyer's agent will cost you no more, and provide you with council and representation that can help you get your best bargain, you should rethink your approach to buying a home.
I would agree with Gordon, a Buyer's Agency Contract is the only way for a real estate professional to legally work for the home buyer in Michigan. Ask your Buyer's Agent to run comparable sales prior to placing an offer, this will give you a range of value.
The home prices vary quite a bit in Plymouth because of the mix of styles of homes. If you have selected a home to purchase your buyers agent should be able to provide you with a market analysis on that particular home. If you don't have a buyers agent I would be happy to help, I am very familiar with Plymouth.