I will chime in with what I have found to a universal truth despite my relatively short saxophone experience. It's not a good idea to buy a cheap knock-off of anything. Not only are they not made to exacting standards, but you may have two other important problems; parts and repairs. If possible it's best to buy a name brand from a reputable nearby dealer, because they'll be able to service your purchase, even if it's used and even if they have to send it out.
Because these products are not always made to best standards, some of them will be ok, others will have serious faults. I recently bought a mouse for my computer. It was half the price of all the others. After two days of intermittent bluetooth connections and seeing that the build quality wasn't good, I returned it. It you buy a used instrument, that's a good bargain but you'll need someone who knows what they're doing to check it for you. Otherwise, used from a store who will guarantee it isn't bad.
In the end, though, I wouldn't buy a musical instrument with no experience but recommending renting it as others have. Even though I have been playing other instruments for decades, I rented an alto to make sure I had the breath and hand and finger muscles to practice and play for hours, rather than the few minutes in a store. You can usually rent to buy, although after 6 months of rental I bought a new instrument.
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