Also this should possibly be edited into the OP but user kingtal0n made a guide in essentially what to look for when attempting to purchase a 240sx.
can be found
here.
A lot of that stuff seems like common sense but I think a lot of first time 240 owners get overwhelmed with excitement when they are looking at an s-chassis that they have the chance to buy.
love will make you blind.
try to shake the heart eyes, go in prepared and decide if it's really worth it.