There are a number of keyword research utilities. Some of them may use data from pay per click search engines to find the actual number of searches for a given keyword. They are thus not accurate. However some other like Word Tracker uses data from Dogpile (major metacrawlers) to give the search results. The result gives you the number of times that keyword has been searched for in the last 3 months. It may also give an expected count for the next twenty four hours.

A very powerful and strong data is maintained by the keyword research utilities. You are likely to get more than 1000 searches for your keywords in case your niche has become quite big. You can also know about the number of websites present in the niche. More crowded the niche; more will be the number of websites.

You can take the help of pay per click search engines for increasing traffic to your website. However you must remember that you will have to pay more for popular and common keywords. Your competitors may pay a lot to get these keywords in case the niche is money-spinning. So you must find less common keywords which are different from what your competitors are using. That's the only way you get to pay less. However the problem with this is that these keywords are not popular and you thus need to find too many for diverting traffic to your website.

The keywords (pay per click ones) will cost even more as your niche become more crowded. Many of your competitors may actually find your keywords by doing some research work on the net. Ultimately this will affect your website's traffic and thus your business.

After some time, your niche will become very competitive. It won't be profitable any more. In such a case, you will have to find some new ways to increase the traffic to your website or you may have to dump your niche!