If you are considering a used bike, I would encourage you to find a well respected local bike shop that sells used bikes. Buying off Craigslist or other used item platforms can be fine too, but if you are just starting and don’t know much about bikes yet, it can be risky.

If you’d prefer a new bike, I might recommend a Canyon. They are a direct to consumer brand so the prices are typically quite good, and you get much better specs for the price than you would with brands that are not direct to consumer.

Canyon have just released an Endurace Allroad which is a fantastic entry-level road bike. The geometry (how the frame is arranged) is very friendly for newer riders, as it won’t have you stretched out in a very uncomfortable position. It has quite good components (parts) for the price. Unfortunately I think it is a little more expensive in the US vs in Europe.

Here is a video about the bike from a cycling YouTube channel that is quite good. They focus on discussing how bikes would work for regular people, not star athletes. https://youtu.be/KoEOayjg0B8

If you’re in Europe and you have access to Van Rysel, they also have some quite good entry level road bikes. The same channel as above (Cade Media) have some videos about them.

Happy to answer more questions if you’d like.

Edit to add: in the video they criticize Canyon for the component sizes. I agree with this to an extent. They definitely exaggerate the scale of the effect. For example they mention a person buying a 2XS being on 40 cm width handlebars and Francis holds his arms out extremely wide. In reality this isn’t a super big deal. My Canyon is that size and came with those bars and it was not a big deal. After a year and a half I swapped them for narrower bars but had no issue with them in the meantime. So in the end - is it the very very best component sizing? No. Is it bad? Also no. It’s fine.