From the movie Rain Man, What were Charlie's motives?

Charlie’s motives to begin with is to discover who he is i.e. he has just found out he has a disabled brother that he doesn’t even recall.

Throughout the film he discovers how hard it is to look after his brother and at this point he asks the question what are his motives? He feel as if his brother is a burden. However when he discovers the true ability of his brother he begins to warm to Raymond.

Towards the end of the film there is a true love between the two characters. Charlie’s motives no longer seem sinister as when he is exploiting his brothers abilities at the casino but he truly wants Raymond to live with him. A possible underlying motive for Raymond to live with him is because of the dependency Raymond has on him i.e. Charlie is no longer a failure and somebody needs and wants him around.

(I know this because i've seen the film several times and have discussed it with a Teacher of English)