What Brandy said should be here:
https://www.newgrounds.com/collab
You should also find it at the bottom of your profile page. The commission offer after made and posted will then appear on your page and in the URL I sent along with other people.
So yes NG is a very commission friendly site. Main challenge will be standing out.
BrandyBuizel
you can mark commission posts on your profile and on your main page it'll let everyone know with a link so you dont have to keep the blog post up for fear of it getting buried, although i would suggest putting all the info there and not off-site as well if able
achiwo
that is useful, thank you for the tip!