TEnsorflow CUDA rerequisites
A CUDA enabled GPU
Well obviously you can't run cuda without a cuda enabled GPU. According to Wikipaedia ' support for compute capability 3.5 – 8.6 (Kepler (in part), Maxwell, Pascal, Volta, Turing, Ampere).'. There is a table in the wikipaedia article that tells you which GPUs are supported. Basically anything after compute capability 3.5 is good.
I'd like to think as a rule of thumb, if you bought your nVidia GPU after 2015 (that's not under £50) you're fine.
Windows
Windows 7 64bit or later (IDK maybe someone has tried to run Tensorflow with Win7 32bit)
Storage Space
Tensorflow package is about 1.2GB, cudatoolkit/cudnn adds up to about 1.6GB, miniconda about 400MB. VS2019 is about 1.1GB if you install barebone, plus misc stuff it'll probably take around 5GB of space