Many will say enom reseller i guess. But the difference between a reseller and parking domain is that for a reseller you do not develop your domain to sell them.
But for parking domain (if you want to earn $$), you are better off developing them and park them in sedo etc. Of course, you can park just the domains themselves but that will very less likely bring you any revenue. Domain reseller can be a fast and easy $$ but parking domains will give you $$ in a long term. Both have their pros and cons.