Yes, they are probably trying to scam you. They'll ask you where you are and will try to arrange a meeting near your place where they will give you the cash there. However, they'll ask you to first transfer the Bitcoin. And you know that they won't be there. Nigerians do this scam using all kind of payment methods like WesternUnion, PayPal etc. Beware. Those 6% profit are going to cost you 100% of the traded Bitcoin. Better look for another deal.