You need to look around the forum more.  There's a hundred threads on BFL that answer a lot of your question.  First off, the SC is up to 60 GH now, and if you put an order in today you'll likely not get it till early next year.  I believe they're up around 10,000+ pre-orders.

As for BTC profit.  Things are going to get messy once all this hits.  Noone knows for sure, but we definitely know that the reward for blocks is going to get cut in half in the next few months, and that would knock your 13 BTC down to 6.5 BTC right away.  Then once difficulty ramps up, it'll just get worse from there.  

I'm not saying it might not still be feasible to do it, but spend some time, do some research and make an informed decision.