Congratulations on your accomplishment.
Just buy what you can afford and get on with life.
Because what you need is experience. Then you will have a better understanding of what actually matters.
I have nothing against Framework laptops, but I think they are suboptimal for a first laptop because they add complexity and over the past thirty years I personally have never seen anyone benefit from buying bespoke upgradable hardware. I am sure someone has, but sticking more memory, more storage and more graphics in a generic box is the only thing I’ve seen work…
…ok so maybe I have a bit of bias against Framework. But a new computer is almost always a better option after a few years than niche upgrade hardware for a niche product.
Anyway, old macs are fine but the hard part is finding a good one that will just work out of the box and will stay working.
That’s true of all used computers in general and laptops in particular.
Someone got rid of them for a reason and unless you know someone or pay a premium price you that reason may mean you are dealing with difficulty, faults, and/or missing components.
Computers are cattle, not pets and a cheap new Windows box is the simplest thing that might work. Maybe a base Thinkpad (that’s the most recent new computer I bought and it’s more than good enough).
Just put some stickers on it to make it look cool. And install Linux if that’s what you know (but running Windows is also the simplest thing that might work).
The future where you can indulge in technical whims is still ahead of you. And no matter what computer you buy you will still have the same heaps of hard work to do.
Good luck.