Question secondhand laptop for engineering student in turkey

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I'm a computer engineering student. Currently I’m using an i3-7020U laptop. It’s still usable for basic tasks, but I’m starting to feel limited in terms of speed, display quality(pwm flicker is very bad, I'm sensitive to tn display), and running AI workloads on CPU.I’m planning to buy a new laptop. I won’t be gaming — my main focus is running AI models locally, mostly on CPU and i like chess, when i open the stockfish, my pc dies. I’m not sure whether having a GPU is necessary, so for now I’m mostly looking at CPU-focused machines.My budget is around $500, and I’m mainly looking at the second-hand marke. Right now I’m considering buying a used Casper Nirvana (like the S100 series) because they are quite cheap. The idea is get like an i7-13620H and upgrade the RAM from 16GB DDR5 to 32GB.I know the build quality and cooling aren’t great, but I can replace the thermal paste and undervolt the CPU (if BIOS allows it). I can also use a cooling pad, so I’m hoping to avoid thermal throttling.My goal is not long-term durability Do you think going without a GPU is a bad idea for local AI workloads? Or is a strong CPU + high RAM enough in this price range?Or should I use what I know to make money instead? My university life is terrible, I'm extremely bored. Instead of buying a good laptop, I could buy budget-friendly laptops, clean them, refurbish them, upgrade the RAM, and then sell them.