What is your son planning on doing? If not mountain biking then something like that bike is a bike that one could ride. I wouldn't use it as a mountain bike as the components aren't really designed for mountain biking, they are designed to hit a price point and really nothing else.

If actually planning to go mountain biking seriously this would be the choice: https://www.marinbikes.com/bikes/202...specifications
It is a really quite decent bike for the price. Air shocks and Deore 11 speed with plenty of actual decent entry level components which will work and last well enough.

If you are looking to spend less look at air forks and 10 speed components and you will generally get something decent.