Refer to this link on the the FinAid website. We have used this calculator to estimate our home value for the Profile. We have typically added on 20% to the figure we get from this calculator as the home values in our town are quite high and even though our house would likely sell for about 450K, the house across our street would go for 900k and 2 new homes are selling for well over 1 million
FinAid | Calculators | Federal Housing Index Calculator
Also reference the book "Paying for College Without Going Broke", they suggest using a price that you know would allow you to sell your home "right away" and to deduct from that any costs associated with the transaction (real estate fees, $ you would need to put into the house to get your price)
We have followed these guidelines and have not had any questions as to our estimate of our home value for the years we have applied for aid at my son's college