Is he really my best friend?

I have a friend that has been my friend for 10 years and I consider him my best friend. Nearly all of my other friends think that I am delusional because they think that he uses me and takes advantage of me. I let him live with me for nearly a year rent free to help him get on his feet and I do help him out if he ever needs it. He is the type of person who has been hurt very bad in a relationship and I feel like he is depressed so I tend to put up with a lot more from him then I would from anyone else. How can I tell if he is really in this friendship as much as me?