depends.. stored in a dry environment, best coverd in a slight film of oil.. they'll be as new,
nothing to do but a general clean ..
stored outside in the weather,
likely they'll be in need of replacement parts and a full tube of elbow grease.
seized piston (water in the cylinder) cause a rehoning of the cylinder bore
and maybe a new piston (surely new piston rings)
bearings, valves.. literally everything can be seized, gummed or bent (tried to start seized engine to violently)
But let's just assume a slightly damp and cold garage as a midpoint.
Likely
carb cleaning,
minor rust removal on the shroud, exhaust and the tank,
cleaning the airfilter will be a good idea,
checking the engine thoroughly is ALWAYS a good idea if it has been stored in an "unknown manner and location",
you might need a new spark plug maybe a new spark plug boot (possibly cable)
chances are the pull cord wants to be replaced as well..
And for sure fresh gas and oil.
Two hours of work on average I'd say.
'sid
PS true Honda GX200s (especially older ones) are AWESOME if the set of three comes relatively cheap just get it; at worst you can disassemble them and sell just the cranks for more than you paid
