How to get a free GPU?

I've been hearing a lot about the benefits of using a GPU for cryptocurrency mining and financial analysis. But, as a budget-conscious individual, I'm wondering if there's a way to acquire one without breaking the bank. Could you elaborate on some strategies or methods that one could employ to potentially obtain a free GPU? Is there a community or forum where people often giveaway or trade their unused GPUs? Additionally, are there any legal or ethical considerations I should be aware of before attempting to acquire a free GPU? I'd appreciate any insights or guidance you can provide in this regard.