Dic: buy in, buy into (ordinary sense not for stock exchange)

• 1: I bought into a company that makes dog food.
• 1: Sounds like a good company. I would like to buy in.
• 2: The committee liked my proposal and decided to buy into my plan.
• 2: Do you think you can get the whole board to buy in?

buy in (to something):

1. Lit. to purchase shares of something; to buy a part of something the ownership of which is shared with other owners.

2. Fig. to agree with; to accept an idea as worthwhile.

VERB | If you buy an idea or a theory, you believe and accept it.[INFORMAL] (=buy into)

• I'm not buying any of that nonsense.
• I bought into the popular myth that when I got the new car or the next house, I'd finally be happy.

...... http://idioms.thefreedictionary.com/buy+in, Cobuild