The kid sees the problem, but cash presents its own dilemmas. If he’s found/caught with more than 5K in his possession, they could potentially cause him problems to the point to confiscation. Guilty until proven innocent.
There are historical examples of methods used to flush out hidden cash, such as the ‘old franc/new franc’ remonitization that the French did after WW2.
The hyper-volatility of cryptocurrency will look more and more appealing as time goes along.
IRS wants you to declare cryptocurrency transactions on you taxes