Buying high PR domains for SEO purposes

Hi,
I want to start my own network of high PR sites as it's a strategy that seems to be very effective for my competitors, they are buying high PR domains (not taking into account the domain name) and then converting the site into a few pages with articles that link to their main sites.
Does anyone else use this strategy and where is a good place to buy expired high PR domains?

See original post by Nathan Mclean