Flipping
Buying items at a low price and reselling them for profit. The core activity of reselling — source cheap, sell high. 'Flipping' implies a quick turnaround, whereas 'reselling' is broader.
Where you'll see this
This term is commonly used on:
ebaydepopfacebook-marketplace
Put this into practice
Shopfront handles the hard parts of crosslisting and inventory sync so you can focus on finding and selling.