How to get search engine under your domain (custom)

Hi, I have some idea of google search API, I guess if you will recommend me to go with that. That I can do my own. But my concern is about the search engine partner with google. I need to know how those many search engines Evan newbie websites are showing ads on their website for any keywords. Is its adsence or any other trick? I am ready to pay the fees for making custom search engine+ You need to enroll me as a google search partner, tell me your price? I am a startup so please bare some discount.