It wouldn't be enough for the boys to live as expensively as they have been living while at home.

Therefore, as fast as they grow up young men, they have to go away into the world, and earn their own money by some kind of work, head work or hand work." Jonas would probably have given Oliver some further explanations on this subject, were it not that about this time they arrived at the mill.
Oliver tied the horse at a post, while Jonas took out the great bundle of wool, and went in.

Oliver followed immediately after him.
The machinery made a heavy, rumbling sound, which grew louder and louder as the boys went up stairs.

Jonas opened a door into a large room, and at this the noise increased very loudly, so that Oliver and Jonas could hardly hear each other talk.

Jonas put down the bundle of wool by the door, and then he and Oliver went in among the wheels and machinery.
There were a great many separate machines at different parts of the room, with girls tending them.