From ground zero on all components? Better do some research on what it takes to make modern casings, primers, powder and projectiles.
This is what "I" would do and it would still be a huge investment for the average guy unless you have some really good marketing skills or a $200,000.00 + line of credit. Really not a lot of money in today's small business world.
First "I" don't see the ability, technology/engineering and/or tooling to procure the raw materials let alone produce primers and powder within the reach of a "small business". To my knowledge, it is not possible to manufacture these items for modern high intensity cartridges in small batches. Further, the licensing, storage, manufacturing requirements (read LAND, blockhouses, chemical containment motes and fire control to satisfy OSHA and the government) for the explosives manufacturing would most likely end your venture then and there. We are not manufacturing firecrackers but top line ammunition that operates at 35,000 + PSI two feet from your face...it has to be a precision operation.
So you would have to get contracts with companies already mass producing components that would be "willing" to take on another wholesaler, for lack of a better definition, and have the capacity to do so in today's market.
I believe CCI would sell you the primers, Hodgdon (maybe IMR) the powder and Starline the brass as more than the others this is their business...but who knows?
I "would" make my own projectiles. This could be handled by Corbin that already sets up small manufactures and with you owning the tooling you could come up with "designer" bullet weights and hollow points tailored to specific barrel lengths and velocities better than the big boys giving you a special niche at your market level. You can get everything you need from Corbin; tooling, presses, jackets, cores and ballistic design help in one package.
Add 2-3 Dillon Super 1050's, packaging which could be as simple as white cardboard ammo boxes with your own computer printed labels, hire 6-8 decent people 2 of which would need to be a combination of accomplished reloaders with a machinist/toolmaker background to keep your machines running within specifications. For liability you would need to send samples of each manufacturing batch to H.P.White or some other ballistics lab to document you are following SAAMI guide lines.
Get all necessary local, state, federal licensing and insurance.
Within 90 days of acquiring the complete setup you could be shipping 100,000 rounds a week. To get and supply, on a regular time line (the only way you will get them), the kinds of sales outlets you need to accomplish the goal of "cottage manufacturer" that is the "go to" supplier to fill in the voids and supply chain lag left by Olin and the others.
This plan could be scaled back many thousands of dollars in the beginning stages by buying the bullets as well as the other components rather than buying the bullet making equipment. Corbin will also put you in contact with small manufactures that use their equipment the last I heard which might result in a "sweetheart" deal for both of you. You could reduce your marketing efforts to gun shows and LGS's to whom you deliver or work your own stand at the show.
This could be done and still have the 100,000 round/week capacity so as your product becomes known you can add the other tooling, packaging and marketing although over a much longer time curve. Depends on what you want and when you want it.
"I" believe there is a place for this type manufacture and wish anyone willing to venture the capital the best.