Yeah the days of getting a respectable entry level new bike for $500 are gone now - and Covid has made it worse. Cannondale, Trek, Jamis - they used to all make a respectable hybrid bike for $55-$550.
But like Captante said you can get a nice used bike for $500. It can be tough not knowing anything about bikes and going on Craigslist and knowing who is trying to rob you blind or sell you crap, but that can work. But if you know a good Local Bicycle Shop (LBS), some of them have real bike enthusiasts running them, and they'll hunt down used frames and other parts and add some new parts and make a nice bike at various price points, including yours. Just, you know, like any industry there are shady bike shops and good bike shops. Maybe join a local cycling group or subreddit and seeing what shops are recommended the most for used bikes.
These are my two bikes. The bottom one is my everything from doing errands to doing 30 mile rides in the city. It's the one I can lock and keep out of sight for a bit and not cry if it's stolen. The top one, not so much. Anyway the frame is a Soma Double Cross - Soma is made in Taiwan and are known to make solid steel frames. Those were over 500 just for the frame new. But I got that whole bike built for $400 at my LBS, with tires I already had. I added the basket and a more comfy seat and upgraded the shifter. The bottom photo is teh $400 bike before my few upgrades.
It would be smart to get a bike with fender and rack eyelets so you can add fenders if you are going to ride if you might get sprinkled on, and for adding a rear rack or basket, if you think you might use one. I was not into front baskets, I always used a backpack. I finally gave in to the front basket and man oh man is it better than a backpack in any kind of warm weather.
You don't happen to live in NJ do you?
edit: btw since you live in a mostly flat area, you do NOT need more than a 1x9 setup. If it's flat as a pancake everywhere, a 1x8 would be fine. In other words you just need 1 ring in the front, not 2 or 3, so no front derailleur, and the 9 gears in the back. So you'd have 9 gears total. Or a 1x10 is even better, but you would save money with a 1x9. A 1x setup vs a 2x or 3x is less maintenance, less weight, and is plenty for riding in the flats plus can also handle some climbing quite well. Most gravel bikes are 1x10 and they ride some pretty serious terrain.
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