I wouldn't consider it a good deal. Of course, I got one back when the going rate was $75.
Rifle needs cleaning, mag missing, bore fair to poor? I wouldn't give $175 for it. I realize I'm cheap, and prices today are way over what they ought to be, for everything, but for what you're getting, I think its not a bargain.
Check out how much it will cost to get a replacement magazine (and know that while all the SMLE mags look the same (basically) and any should work, you might have to do some work to get a replacement mag to function properly.
Also be sure NOT to get one of the mags for the .308 models, as these will not work in a .303. The .308 mags have a sharp edged, sloped flat bottom, the .303s have rounded bottom edges.
If you are going to get it, see if you can get the cost of a mag taken off the price, at the least. OR, tell the owner you'll pay $175 for the complete rifle, and let him get the mag and put it in.
Also, the bore might be only "fair" but that doesn't automatically mean it won't shoot well enough. I got one, was told the barrel was "shot out", and that rifle put 5rnds of Rem 180gr .303 into an inch and a half at 60yds, from a kneeling position. Told the previous owner that, and he hmmpf'ed and said, must have been the other one he had that was shot out....