Vendor qualification isn’t easy but it’s also not especially difficult as long as you’re an American citizen with no criminal history. Figuring out the paperwork is half the battle.
Past that, the hoops you'll need to jump through depend a lot on which department is handling procurement. If you look at defense-related contracts, you'll also have to go through personal clearance (which can be difficult by itself at higher levels).
Being selected as a vendor, on the other hand...