Honda sohc 4 parts are plentiful, and they really can be made to run pretty reliably. Well, as reliable as vintage bikes can get.
1K is a good price, if its running, titled, and most importantly maintained. Modern bikes can really spoil you when it comes to this cause getting all 4 carbs synced up and running right can be a pain.
every one I've swung a leg over tended to develop a leak around the head gasket. Make sure to check for leaks there cause if there is you'll probably have to drop and resto the engine. I hope you know how to work on your own bike.
Without seeing pics and or more details, 1300 could be a good deal if you are planning to ride it as is, or mod it and ride it. If you are looking to flip something for profit, unless it is mint, keep looking.
There are lots of cb750s out there, but they aren't making any more of them, tons are getting parted out or cafe'd, and the one you describe is one of the currently more desirable singe overhead cam (SOHC) models.
If it runs and rides with title, your potential downside is pretty limited when spending only 1300 to start with; could probably ride it for 5 or ten years and sell it for the same or more...that's what I like, free ride time!