How could you define a person who consistently offers help in growth and development in others and expects nothing in return?

hahahahahHAHAHAHAHAHA

a parent

A teacher.

I would describe that person as Scott Peck (et al) has described them: loving.

Love
n.
"The willingness to extend [or sacrifice] one's self for the benefit of another's growth."--M. Scott Peck, MD

Someone who loves like a mentor, acts as a teacher, and gets something out of it - a sense of achievement, or satisfaction, or something.

A mentor of some sort. 

In a none authoritative position? I might describe them as hopeful, genuine, selfless to a fault, and insecure or uncertain of their worth. I can't think of any one word whose description sums it up.

An odd person.