Questions about Google Adwords?

[dermot]

Legal, insurance & Asbestos (mesothelioma) are among the highest CPC in adwords. If you log in to Google Keyword Planner and enter the keyword, "mesothelioma" it will show a CPC of around $250 - $300. e.g. a quick search on keyword planner for "mesothelioma compensation" gave a CPC of $268.95.
If your CPC is £50 then Yes you have to pay £50 every time somebody clicks on your ad.
Question 2 I am unclear about. I seems like you want to place google adsense ads on your site. You will not get paid just by people visiting your site. You will get paid when they click on an adsense ad on your site. The ad google places will be relevant to the content of your site.
How much you earn per click will depend what type of ad google places on your site.