It really is hit or miss though. I mean, most of the time, the customs let people in. But if they start fishing for information, and find something they don't like, you're powerless. Like, they probably asked him the purpose of his visit. He probably said friend. They probably asked, how do you know this friend? He likely either lied (because the whole system makes you want to lie to avoid getting in trouble..its so fucking stupid). or said he met her on MySpace. They probably then asked if he had ever met her before. Once he admitted he hadn't met her before, they were probably digging, asking him more questions and decided he was a 'threat', even if he really isn't.
How much money did he actually bring? How long was he suppose to stay? A week? Two weeks? The longer the visit, the more suspicious they seem to be.
I crossed the American border with 5 bucks once lol. The guy at immigration said "How much cash do you have on you?" I was going for three or four days, can't remember, but I said "5 bucks" He said "5 bucks!? How are you gonna afford being here for 5 bucks!?" I told him "I have a credit card" He then asked me if I had ever been arrested. I said nope, and he let me through. See, you can never tell.
Sounds like they probably told your brother he didn't have enough evidence to show he was returning or could support himself, or they didn't like the fact that he met a girl online and was coming to see her (which is dumb because people do it all the time), and he was probably embarassed, so he just said it was lack of funds. I mean, they CAN turn you away for not having enough to support yourself during a trip, but I don't think there's a definite amount.
Anyways, here's what the official guide to visiting Canada says, show it to your bro lol.
Visiting Canada: Who is eligible
To visit Canada, you must:
* have a valid travel document, such as a passport
* be in good health
* satisfy an immigration officer that you have ties, such as a job, home and family, that will take you back to your country of origin
* satisfy an immigration officer that you will leave Canada at the end of your visit and
* have enough money for your stay. The amount of money you will need can vary with the circumstances of the visit, how long you will stay and whether you will stay in a hotel or with friends or relatives. For more information, ask the Canadian visa office in your country or region.
http://www.cic.gc.ca/english/visit/apply-who.asp