A friend doesn't sell another friend a miner that costs less than half the price the D3 is going for direct from Bitmain, and regularly sells for even less than that. You're getting ripped off buying a D3 at this price, and according to Nicehash's calculator, you're making roughly $100 per month without electrical costs, so if you're able to secure a D3 near Bitmain's price it isn't a bad buy. Just make sure you can accommodate for the power and noise that these things make, they're extremely loud.
Yes, the PSU (APW3++ for example) also costs money, but it's not worth ~$400 dollars if you take Bitmain's D3 price off $700.
Here is a listing for the D3 at $250 + escrow on the forums. Much better deal than what your "friend" offered.Actually sold out.
Here's another listing.