Also,
Mids are Issued a card referred to as the Midshipman Card- What it is is a direct check-card for their held pay account.
How this works is: Each and every midshipman on the yard is paid $990 per month from the Navy. As 4th class, you only see $100 per month, every month (except July and August, which is only $50 per month). The rest of the remaining $880 is used to pay for laundry, haircuts, food, life insurance, class fund, and the big kicker- to pay back the ace loan. Any remainder after that goes in to the "Held pay" account which is accessible using the Midshipman Card, and can only be used to purchase standard-issue and necessary items I.e. books, soap, and uniforms.
Every now and then, the "held pay" account is liquidated in to your paycheck, and you get some of the money back.
It is a really confusing system, but just know that in the end, 4th class get paid $100 per month, 3rd class $200, and so on; of that, none of it needs to get spent on anything. Does it get spent though? Most likely, yes.