Become Rich

How did Heathcliff become rich after we ran away? What did he do?

I’m currently reading wuthering heights and a bit confused as to how Heathcliff became rich after his running away. Was this part of the book I accidentally skipped over?

If I remember correctly, he joined the military and saved up his money. I also vaguely remember something about intelligent gambling and giving loans with insane amounts of interest to strip the money-borrower dry.