Students who want to build a game, and maybe sell it.,Commercial use, students, what is allowed?

Not exactly, please read the literature posted above carefully, specifically this part:

THERE ARE TWO WAYS TO GET UE4 INTO STUDENT’S HANDS:
Any student can personally subscribe for $19/mo, install the software on all of the student’s own computers, and use it for any combination of educational purposes (for free) and for selling commercial products (paying Epic 5% of gross product revenue).
Any academic institution can obtain one $19/mo subscription and install the software for unlimited use by anyone on all computers owned by the institution, such as university computer labs. Anyone who develops a product in this environment can later decide to sell it commercially by obtaining a personal subscription.

So I guess it would be free for you if your school decided to purchase a subscription, otherwise you will personally have to pay the subscription and any other people working on the project will need to as well. However you can cancel your subscription at any time and still continue to use UE4, you just won’t receive updates.