Is it a good idea to make money buy selling beauty products?

what i mean is that i would buy beauty products from marshalls/tjmaxx and sell the item high enough to make profit but low enough so that its cheaper than retail price. marshalls/tjmaxx has brand name stuff (like chi, tigi, elizabeth arden for half the price). im planning to sell it through my blog. should i tell people where i got the products? is it dumb if i do? i want to be honest.