One request does most of the work here, and it is the one sellers skip.
The questions
"Can you measure the chest flat, with the tape on camera?" And whatever else matters — shoulder, sleeve, length, waist, inseam. Sizes are not comparable across makers, countries or decades. Non-answer: "It's a medium."
"Has it been altered?" Taken in, let out, hemmed, sleeves shortened. Not a fault — a fact that changes what the measurements mean.
"What does the composition label say?" Fabric decides drape, warmth, shrinkage and washing.
"What are the cuffs, collar and underarms like?" Where wear shows first, and where it is most often cropped out.
"Any marks, and where exactly?" Located and sized, not "minor signs of wear".
"Does it have a smell?" Storage, smoke, damp. It survives a parcel.
"Has it been washed?" And by what. Buyers in this category ask, and good sellers volunteer it.
What protection covers
Measurements materially wrong, undisclosed damage, an alteration not mentioned, a different garment than shown: seven days from delivery. A garment that fits differently than you hoped, when the measurements were right, is not — which is why the first question is the measurements.
Questions people ask
What if the seller will not measure?
Bid as though you have no fit information, or do not bid.
Does pilling come off?
Some, with care. Assume it does not.
Is second-hand clothing hygienic?
Wash it on arrival by the care label, and ask whether it has been washed.
More: buying menswear, describing condition.