@Sampor27, while I don't have a problem with buying secondhand, upgrades, especially if they're not needed, would make me run a mile.
For further context, where did you see them advertised ?, have you got links ?, because for me, looking at the seller can be as important as whats written in the ad, feedback, postcount, quality of posts etc, will tell me if the seller is trustworthy & knowledgeable.
For example, if I look at a gun for sale that's been "upgraded", & then I look at the sellers posts & one mentions "using .30's will burn out your mosfet" 🤪, I won't exactly be inspired to reach for my wallet 😏