As far as I know Active Rain has a free basic account. The paid account has more benefits but there is a basic, paid version.
Check out the website for more info
http://www.ActiveRain.com
Yes, I am sure you can gear the blog toward buyers if that is the market he wants to reach. Take a look at the Active Rain blogs and see what other write which will give you a good assessment of what people are reading. Sign onto the Active Rain newsletter.
Janine