I'm sure a few LG owners will chime in with personal advise and pricing guides.
There are certain things you want to see on any purchase like this, be it a hammer or any old tool/machine:
Is is running and will the owner demo it doing the type of work you will use it for?
Are there any welds or repairs? If it has been fixed, that means it has been broken. Sometimes that is OK and sometimes it is not. The repairs should be done right if they are present. If the repairs look new on an old machine.... be very cautious.
Is everything there? It is easy for the seller to say ( eg), "All you need is the main spring and it will be like new!"....but is that spring available????? The other thing often said is," All you have to do is clean it up and do a bit of restoring....". This line is used by people selling old cars,too.
Condition is everything. Paint is not condition, though. Many sellers will blow off an old tool and slap a coat of red paint on it and say it is in "vintage" condition. Ask the seller when it was last maintained/serviced/overhauled, etc. I would rather see a well greased/oiled machine with a good layer of hard-use dust and grime than a sand blasted mystery machine with a shiny coat of paint. If the bearings and moving joints are worn or dry and unmovable, expect lots of re-building. Also be aware that any sandblasting could have ruined the moving parts.