There are over 650 PPC search engines at the time of writing (PayPerClickSearchEngines.com) and almost all of them belong in the Tier 3 category. The Tier 3 PPC engines are small providers of pay per click advertising that usually do not feed other search sites with PPC results, but only show adverts in their own web properties. Setting up an advertisers account on a tier 3 PPC search network is often not worth the time and effort, because the amount of visitors through these search engines is likely to be minimal. (Kent 2004, 294.) Nevertheless, some of these networks do provide a decent amount of traffic with a very low cost per click, so one should not ignore the tier 3 PPC providers completely. Reading webmaster and search engine -related forums can give an idea, which small PPC engines may send valuable traffic.
Some PPC networks are specialized in an industry or geographic area. These networks may be very worthwhile for some advertisers, because these pay per click providers may be able to deliver relevant traffic at a very low price. For example, a real estate agent in Arizona in the United States may find the following sites suitable places for PPC adverts: Arizona Life: Online Guide to Arizona (http://www.azlife.net/) and a real estate search engine, HouseReal (http://www.housereal.net/).