If you'd like to get an estimate to do the build out you can contact Doug Trowbridge at Parr Lumber. He can give you the cost of materials. You'll just need to let him know the square footage of your current layout and how much you'd like to add up top. I can ask a couple contractors I work with to see what the labor would cost.
You're welcome to send me a message regarding where your property is currently located. I can give you an estimate based on sales of what your home might be worth with the new addition.
My excellent realtor for last 2 years there is Chris Aldrich, REMax, 503 999-3049, is very good at looking at a house differently and seeing what it could be. (I trained him!) He also knows more about goverment reposessions than anyone in Salem and can help getting an inexpensive repossession and knows very reasonable trades people. I have bought and renovated 12 properties with hin in ayear and a half! He's best I have ever found!
Good luck on your project, Jim