Ninja 250 is the standard answer. $1-2k in my area used. OTOH, to give a good answer, more info would be needed. Ie: age, height, weight, riding & driving experience, preferences. Even then the answer would probably be then Ninja 250 unless you plan on buying new, and your comments indicate otherwise.
I don't like cruisers, and especially not for a beginner bike, so I wouldn't recommend one. There are a number of them out there, if that is what he really wants. A TW200 is also a great beginner bike that can pull some fairly serious trail duty, and can be a lot of fun for an experienced rider who accepts it for what it is.