Slight play in the steering could just be worn bushes or track rod ends (not difficult to fix) or could be a bit more of a bugger if the steering box itself is worn.
As for rust, every landy more than about 3seconds old has rust on it somewhere. So don't be put off just because you find some. The important bits are that it's structurally sound and the rust isn't too bad on the more difficult parts to fix, like the bulkhead etc. And that the engine, gearboxes and axles are mechanically sound.
I don't like to be the guy that says do a search, but there are many discussions on here on what to look for when buying a landy. I did come across a really excellent guide someone had written up, im sure youll find it, its well worth a read.