This is a big compressor, larger than most dive shops would own, unless they are filling hundreds of cylinders per day. I am a Mako fanboy and have worked on a number of -09 blocks. They aren't the most reliable in the world, mostly because they are either used to death, or used for something other than air. If this is truly as described, it's a smoking deal. Even if it were stripped down for parts, it's a great deal, but you aren't in the stripping down for parts business. This is a far larger compressor than anyone in the world needs for personal use, which leads to it's own problems. Without a large bank to charge, the compressor really never gets a chance to warm up, leading to early fatigue of parts, especially valves. It isn't something I'd recommend for a daily user, I wouldn't even have it on a liveaboard.
Good luck with it.