This is not a DIY job. Talk to a few different local well diggers and get written estimates before proceeding. Also, check with neighbors to find out what success they have had in locating water. Some areas are better than others.
Around my summer home, (Chesapeake Bay, Maryland) finding water is mainly hunt and peck guesswork.
Basically a pro helps pick a spot and just starts drilling. They continue down until they strike water.
In my neighborhood, some wells are as little as 30 feet deep and others are several hundred feet down. Sometime people drill several hundred feet down and come up dry, only to restart in a new location, often less than 50 feet away and then sometimes strike water almost immediately.
BTW, drillers prices are based upon the ultimate depth of the well. There usually are no guarantees that you will in fact find water.