Building contact / prospect lists

Hi Everyone, Found a year old thread on this and wanted to refresh - does anyone have experience hiring someone on Fiverr or Upwork to build a prospect/contact list for proprietary outreach? What best practices can you share? What databases did you use for finding specific contact information? Also, if there are any specific people you'd recommend, would love a referral.

Related: I hired someone on Fiverr to create my LLC logo and am very happy with it.

Thanks!