I was able to get "Crazy Unbelievable Success" doing the cheapest (60000) search using the cheapest agent (8000), but spending all of the money I had (almost 5,000,000,000).
Japan
Neo Japan Kinki Branch
Homeless Man
4,900,000,000
On my first try with the above selections, I received the "Crazy Unbelievable Success" result, some crappy items, and a Tin Toy treasure (probably can be sold for money). FWIW, I also didn't have any success boosting items equipped.