Unless you are going to live in one side, you need to be asking about the rents. A capitalization of about 10% should guide you to what it is worth once you know the rents.
Let's say you get $700/month each side. Multiple by 12 months to get your annual and then divide by 10%. I show a list of about $168,000 would be fair market as an investment. If you can grab it for less then congrats! You win!
Cheers to investing in Real Estate!