How can you use the word leech in a sentence?

Bob kicked Joe out of his house because he felt Joe was a leech; he ate Bob's food, used his utilities, and never seemed to have the money to pay up when the month was out.

OR

Doctors in the middle ages would sometime put a leech on a wound in the belief that, by sucking blood from the wound, the swelling would go down and it would help the wound to heal.

OR

I found out my neighbor did not passWord-protect his Wi-Fi connection, and since it extends to cover my property as well, I've been leeching off his bandwidth for months!

Hope this helps!