Two niche keywords I found get a combined 300k searches a month. Theres only 1-3 bidders for these two keywords. However if I wanted to put up adsense how would I get any money if there arent any advertisers paying for ads? Would google just end up putting non relevant ads on my site or none?
How is the competition for the keywords though (you need to consider this also). You may get a mix of relevant and irelevant ads... since there are only 1 - 3 bidders (are you sure? That's a very low number.)
Before selecting a niche you should always see 2 things, 1. Searches for that Keyword/day 2. Competition for the keyword If you Searches are more and Competition is less then you must select the niche as it will be easy to get into top 10 in Google Easily