If you're broke, get a refurbished/used Nvidia P40. Same amount of vram as a 3090, between 4 and 10 times cheaper depending on how cheap you can find a 3090.

Granted it's slower of course, but best bang for your buck on vram, so you can run larger models than on a smaller bit faster card might be able to. (Not an expert.)

Edit: if using in desktop tower, you'll need to cool it somehow. I'm using a 3D printed fan thingy, but some people have figured out how to use a 1080 ti APU cooler with it too.