I'm looking at building an AR from Model1 too, but I was thinking about milling one of the DSA 0% forged lower blanks. I might just buy a stripped lower instead and be done with it. It'd be a helluva lot easier.
Model1 description says "All kits are complete - less stripped lower receiver" under all the variant types. In the detailed description it says the lower parts set is included. The detailed description say it includes everything but the actual receiver. The upper is assembled and headspaced, so all you would have to do is put the parts in/on the lower and you're finished.
The kits start at $415.00 (I think that was the cheapest) and up depending on options and kit type. Add the $80 to $150 for a stripped lower (+FFL fee and shipping) and that's your cost. I think $550 is a pretty good estimate for building one from these parts kits.