I usually buy used refurbished components from reputable stores. Likely eBay too. Being in the tech industry I realized how mind bogglingly cheap even slightly “old” hardware is. If you want an entry level/mid tier you can buy a used office PC with an i7 8700k or something (make sure that specific model has GPU power overhead) and buy a refurbished gtx 1080 ti. Make sure to add an SSD if it doesn’t have one already. In fact skip the HDD and buy a high capacity SSD, they are cheap nowadays.