Personal shopping sources?

I have seen a lot of personal shoppers on social media and they sell to proffessional footballers and celebritys. Its mainly sneakers but also designer clothes. Upon looking into it, it seems they can source designer brands for under retail and rare sneakers within hours but I can't understand how. Is it just a good network but then how do they get the cheaper desginer, is high-end designer wholesale a thing? I've been having a hard time researching how to get started and wanted to know if anyone can drop some tips or point me in the right direction. My first thoughts for the shoes are botting or knowing botters, is this right?