Tax implications of free items received and resold

I am a member of a program in which I am given goods (at no cost) in exchange for providing product reviews for those goods. The company sends me a 1099 for the fair market value of those goods, for me to report as taxable income.

 

Thus far this has seemed pretty straightforward. But what If I decide to resell those goods, as used items, once the required waiting period has elapsed? What are the tax implications of those sales?

 

As an example, say I receive a printer with a FMV of $100. That $100 counts as income and I pay income  taxes on it. For the sake of argument, let’s say I pay $25 in income tax on that $100. 

Later, I sell that used printer to a third party via a private sale, say for $50. How do I account for this $50 in income? Are there other implications I may not be aware of? Would I need to somehow arrange to collect state sales tax on the items sold?  How would I record this activity in TurboTax?