You can make $200-$400/mo. selling links on PR5 adult pages with low traffic. Buyers usually want less than 20 links out.
Just run ads at
http://linkadage.com and
http://findtextlinks.com
I've seen PR5 pages sell anywhere from $350 to $1500. Be carefull buying them. Its very easy to pump up PR by buying links on a site, then dropping them after ist sold. Make sure the backlinks are ones that will remain.