I've been lucky enough to find a used series 70 mkIV colt in cali for a fair price.
What should I inspect to make sure I'm not getting a broken hunk of metal?
The gun is finished in Nickel, looks very used, but would probably shine after a good cleanup.
thanks for any suggestions

Other than the regular check the bore, look for obvious damage type things, take a very close look under strong light to look for frame cracks.  They are even harder to spot with a nickeled or parkerized gun.  Look particularly in the area around the slide stop pin hole, the frame rails at all points, but especially in the area above the silde stop cutout, and look also just forward of the slide stop pin hole at the dust cover (this last area will not affect function, but definitely lowers the value).

As far as looking very used and shining up, nickel Colts tend to look pretty nice even after a lot of use.  It seems rather odd that it would look beat up.  One old trick for getting nickel to look good is to rub it with olove oil.  You can let it sit for awhile, and rub the stuff off.  Try a few application of this, and you'll be amazed at how areas of staining, especially in the grip safety area, will disappear.  One last consideration is if you intend to use this as a base gun for customization.  It's fairly easy to remove the nickel with Brownelss room temp nickel stripper.  They advertise it as removing nickel in as little as 30 minutes, but in reality you need to let the gun sit for a couple days in the solution, and also have access to a blasting cabinet.  Good luck.

Thank you very much for your advice gentlemen