It works out well only for in demand items. For example something such as RN4 right now. I have done it many times but not as a reseller to be specific.
I am fascinated to try out any good phone that launches so I try my best to get hold of it in the first sale, use it for 2 or 3 days and sell it at cost. I was always able to sell it off even after using it because the device is in high demand at that time. If you want to sell it at cost the only way you can make profit is if there is some website offering cash back or there are some launch offers you can make use of.
I specifically used to get devices to sell them at high prices back during iPhone 2g/3g/3gs/4/4s days and few Android phones. I sold each phone with several thousands of profit by getting them from US. The latest I have done was with OnePlus 2 where I sold 5 phones with a profit of around 10k per device at an average in the very initial days.
But things are not that rosy right now with device availability being lot better so do watch out before betting on such things. Give it a try in a small way to begin with.