Zolio

Sdeangelo, I thank you eternally. I have been trying to find out the name for this book for two years (Not excessively searching though). Now I can read it again.

Instinctively I thought of the Artemis Fowl series, which has a fairy underground base in London. Probably too sci-fi for your request though.

I'll try to go into as much detail as I can: The book is set in Mexico. It starts out in a shack with a little boy, and a grown woman (20-ish?) taking care of him. One day, while she leaves to get something, two kids come over. They want to play. The kid inside the shack wants to play as well, so he breaks through the window and falls unconcious. The kids take him to a nearby mansion where they live. The staff recognizes the boy for who he is (Which is called an invalid). They treat him like an animal, until the girl taking care of him finds out. The invalid kid develops a love interest with the daughter of the owner of the mansion. He also develops a friendship with one of the guards. The kid is also friendly with the old man who owns the mansion, but he hears that he is an awful person. Later the kid figures out that he is essentially extra body parts for the old man, and the man is somewhere around 180 years old. After the old man dies and takes his staff with him, the kid tries to escape Mexico. After a lengthy journey and a task of working in this one town near the border of USA and Mexico, he escapes I believe. If you have read the book, the detailed story above is sufficient enough to help me out.