if looking at convertibles, Arent there lower mileage ones available? Look at maintenance/MOT/Service history. Some early years 2009-2013 were prone to steering lock issue. So check the fuse isnt still plugged in. Look up "steering wheel lock 370z"
While the convertibles are nice, I found most places replace the roof. But mechanically it can be difficult to find someone to fix it if it stops working...if you arent DIY esque or a dab hand at repairing things
I usually use clickmechanic when buying cars to have it inspected. For extra peace of mind unless you know a mechanic yourself. So you know what issues you might have to sort if any