Mongoose Legion L100: https://www.amazon.com/Mongoose-Freestyle-Beginner-Featuring-Available/dp/B07GNDF1HH?th=1

It was 250 a week ago. The price fluctuates up and down because Amazon uses multiple vendors.

This is the cheapest 21" bike worth getting. He needs a 21" frame if he's 6'1 and trying to find a bike cheaper than 250 will be a serious pile of garbage. Either save up to get the Mongoose or wait for Amazon to change vendors and the price to go down...