If it is listed with a Real Estate company, a Realtor can take you through it. If not, you might call the bank who holds title and ask them about it. Also, you can take the address to the county tax assessor and get a property card that will give you square footage, age of home, etc. and tax records that will show you the tax assessed value. But remember, tax assessed value and appraised value are typically not the same as the two look at different things to get a value for the home.
You may also want to take into consideration the condition of the home and location when making an offer.