For me the key question is "Has water
pooled inside the boat?"
Look along the stringers, down the frames etc.
If the boat has been "foamed" is it possible cut away the foam (get the owner to do this!) along the stringers, particularly in the bilge
areas and around hatches/portholes.
If salt water
has sat inside the boat this is much worse than fresh water
Some Roberts have been built with full width steel bulkheads. If this has happened then the bottom of these bulkheads can be a real rust trap.
Now check if water can drain freely through limber holes to the bilge
Bad rust can be a deal killer unless you can take the boat from the water and cut and weld it for a reasonable price
Now it becomes a judgement call. Look at the price
, how much it costs to fix and the level of equipment/fitout/finish.
Some steel boats have been built very cheaply so remember that the hull
is only about 40% of the complete boat.
Once you have done this look for a surveyor
with experience in steel boats.
If you can find someone who has owned a steel boat for a while the their comments may well be worth listening to.