Please help me understand HML costs

[Benjamin Cowles]

So I spoke to a HML today regarding a potential deal that had (our) offer been accepted would have been at a purchase price of $400k for an ARV of +/- $550. Seems like a good spread no? 40-50k rehab, up to 7k holding costs(6months @ most) = maybe $480 left over? What could closing costs when we sell be, another 10k? So $470. 12% HML for half a year max? Quick calculation... Shouldn't that be around 7k if interest only til payoff? Oh, and optional realtor to sell it for discount 3%, what's that, 17k, so how bout 25k more = $445. Hmm... Looking slim at worst at 45k profit to split between myself and partner. But oops, HML points out the 80k +/- loan (no rehab) with closing costs will cost around 20k, and not even rolled into loan. Whoe, stop right there... Apparently I've not done enough reading. He went into it but it was just a blur. How much does hard money cost? I think he mentioned doc stamps. Isn't that a seller's cost? What else was he talking about. That little 12% apparently is just a small part. I would have kept him on the phone but he seemed in a rush. Can someone explain?