The topology of the shoulders and belly looks questionable.
I’ll put some work into the shoulders but as for the belly I might just leave it as it is, I might work away a bit on it but I don’t think it is a issue.
I would also pay attention to all those 3-poles on the face, I think there are quite a few more than you need.
The Fore head “Poles” (or faces) are there for animation purposes.
There are both Game and High Detail character models with this amount of forehead faces.
it’s a more accurate representation of the actual form and can help reduce your polygon density where so much just isn’t needed. You’ll be able to more easily/accurately get the right shape when adjusting the body proportions.
there is a software that makes base meshes for free, its called makehuman and was developed in collaboration with blender in the start. That’s what i use for base meshes. http://www.makehuman.org/
Yes. Sorry to say, but if you intend to make money selling meshes, you’ll need to make something more detailed or specialized than the ones in makehuman. Try full clothed/rigged/textured character with normal maps, or HighPoly sculpted version, Non-human characters etc…