Is this a decent lower?

The DS Arms lowers that I have seen/worked on have been good in terms of both fit and finish (never seen one completely assembled from the factory, so I can't comment on the quality of the lower parts/stock assembly used by them). All of their stripped lowers I have seen/worked on have been within specs and functioned without issue.

If those are actually in stock and available for that price ($250), then I'd call that an good deal in the current market. At a minimum, its a decent starter for someone just looking to get into an AR. Plenty of options later to upgrade in terms of better triggers, stocks, etc. for the lower, and he can assemble whatever type of upper(s) he likes.
 
Appears to be a generic forged lower with a standard LPK installed. As far as the price is concerned, personally i think it is a little high, but pretty much in line with the current available lowers. If he wants to save a little he can buy all the components individually and assemble the lower himself. Or plan on spending the same amount and assemble with higher quality parts.

This is all somewhat depending on the intended use of the firearm and ultimate goal as far as cost and fitment. If the ultimate goal is to build a precision gun then there are other alternatives that could be utilized. For a general range/fun gun and for the convenience of it already being assembled, it is not a bad option.
 
$250 for a complete lower with 6 position stock. You can't beat that anywhere right on. Well, maybe with a $79 plastic lower and PSA build kit.

Better call to see what the wait/back order time is.
 
Most any well-constructed lower will work about the same, unless you want an ambi bolt release or some such thing. Looks like a pretty good deal considering the current state of things, especially if you can actually get one.