I would go for it. No need to invest the entire thing all at once. Buy a few items and see how it goes.
As far as the dongle, I would go with a prepaid plan. That way, you are not locked into a contract.
Also, there is no reason to tell ANYONE that you have $1,000. Too many people get ideas...
Lastly, it seems to me like you have a mild or worse case of risk aversion. Sometimes that can be a good thing, but you should not let fear paralyze you. If you have done your research and feel confident that you can buy and sell a few items at a profit, then go for it. If it seems iffy, then pass until you find a better product.
Never be taken in by a salesperson or sales language that tells you that you must "act quickly" or the deal will be gone. Trust me, the world is full of deals. The trick is to pick the good ones and steer clear of the bad ones.
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