500 dollars total is a very low budget for an PC, especially one that needs to be used for training/running large language models or image generation models. These machine learning applications are extremely hardware intensive, and as such, it would not be possible for me to recommend a PC for your application at this budget. 

You might be able to find a good deal on used enterprise hardware for a low budget, however the market for these fluctuates greatly. Another option you can look into is renting a powerful computer in the cloud to train and run your model, however, that comes with its own set of technical challenges for an individual.
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