Out of curiosity - which GoPro have you specifically looked at ?
A lot of the off brand ones that I’ve seen/used aren’t the greatest in quality in the video/photo let lone the build - so might work for a while but then will break, then not having customer support to help when those issue occur - or like I said the quality of the video/photo just sucks.
Another one to look out for might be the new DJI Osmo Go series (I think that’s the name).
One thing that might be worth waiting for instead of going second hand would be Black Friday - amazon usual have go-pro sales on during then.
The reason to why not second hand would be the lack of warranty etc.