Get yourself a buyer's agent. That agent will be able to help you, especially in determining a fair selling price. Buyer's agents should review the property and complete a mini- market analysis to help determine where the property value is at the time you are making an offer.
As far as the flooding goes, you should ask that specific question of the seller. And ask them to put their response in writing. As a matter of course you should ask that the seller complete a "seller's description of property" which lists all kinds of information on their knowledge of their property. So it will tell you if they did any upgrades to the home, if they know of any problems, etc. In other words, anything that materially affects the value of the property.