1. 27" wheels
2. Steel wheels
3. Nutted axles
4. Hi-Tensile steel frames
5. Rust


The only item on this list that is not a preferential issue is rust.
But rust in small amounts can be cleaned and therefore only quashes a deal if extensive.
The other items mentioned are completely reliable and serviceable if they are of quality.
While most riders who post on this forum prefer to have chromoly frames, alloy wheelsets and quick release hubs they are not absolute necessities for a usable ride.