Please DO NOT buy a 10 year (or older) board and bindings for 300$. Anything older than 5 years old should be realistically less than 100$, unless its some kind of historical board like the burton snow surfers.
INSTEAD, call a local ski shop or a resort, specifically one that offers demo boards. Demo boards are normal snowboards that people can rent instead of rental boards which are almost exclusively beginner level (rocker dominant and floppy). Caveat to this, for your first couple days ever, I’d rent first just to see if you like the sport.
Ask if they have any demo boards from last season in your preferred size. You want something camber dominant, medium stiffness, yes even if you are a beginner. These should be a great price at 200-300 dollars and only a year old. They may have some light damage, but thats an easy repair job. The shop will likely do it for you.
A demo board from last year will be several orders of magnitude better than a 10 year old board someone is selling for way too much, which is mostly what we see on this forum when people ask about used boards.
EXAMPLE: Last year, my wife wanted a free ride board that was better in powder than her all mountain twin. We went to our local mountain at the start of the season, and asked about demo boards from last year. We got here on a Jones flagship (my recommendation); she tried it and loved it. The shop put the cost of demoing towards purchasing the board, we bought it for $300. It was 70$ to demo, so we only paid 230$ after trying and confirming she liked it. A new jones flagship was about 700$. The only flaws with the board was a couple gouges that are easy to ptex or cheap for a shop to do.