Were these totally new computers - from known brands - acer, hp, compaq, etc?
or were they ones he built himself? Or rebuilt/ refurbished?
- which is fine - but could be cut rate parts inside or quality parts- hard to tell unless he gives you some info & paperwork about the inside parts...

what kind of warranty? - would he provide repairs himself if needed?
does the place look legit or shady/fly by night?

you'd have to compare the CPU speed - the ram - the drive size
it would be nice to know the brand of motherboard that is inside if they are self built.. Intel, MSI, ASUS...