There is plenty of information on robotics in Baltimore
on this forum.
There was even a battlebots competition in Baltimore about a month ago.
You can generally expect to spend about $50 minimum on a robot, and another $50+ on tools and such. If you think your boy will not lose interest, invest in quality tools that will last many years (it'll cost more in the short term, but save money as they won't break in the long term). Robotics is inherently expensive, but engineering degrees result in high pay checks later in life - so consider it an investment
The $50 Robot
, as waltr said, is a good beginner project designed to teach not only how to make a robot, but to also learn all of the fundamental skills needed to go beyond simple kits. It might be a little over his head, and a bit dangerous with the soldering iron, but with parental supervision it'd make a nice father/son project over several weekends.
And if he/you ever gets stuck, have him post his problem here and someone can help. I would say about 10% of the people in this forum are his age, while 1/3rd are under the age of 20. Age really doesn't matter if he is serious about robots . . . and searches google before asking questions