Hobby income & expenses.
Bob is absolutely on the ball about this. There are clearly distinctive features of businesses that are designed to produce profit and hobbies that may, on occasion, produce sales income.
The bottom line for businesses is that losses can be fully deductible. That would seem to be the major focus for persons actually in business (and doing all the financial things required for a business to succeed). Hobby losses can only be declared up to a limit.
The concern for people attempting to run a business is to make certain that they are keeping the financial records and doing the planning that any business requires. There is unlikely to be any
financial benefit for someone who tries to run a business as if it were a hobby.
If ham radio is a hobby, which for most of us it is, your income from sales of gear should not be a problem Federal tax-wise. State rules on sales and related taxes will vary, but I very much doubt that any state which collects hobby sales taxes will have the resources required to enforce such. It would cost an economically-stressed state a lot of money to try to collect hobby-related sales taxes.
Wealthy states with huge budgets don't enforce sales tax requirements. They get their income via significant, highly-productive, income tax legal machinery.