Personally, I think trying to become a spoke manufacturer is a bit over ambitious
unless you had a metal working factory.  If you could by full-length spokes to thread
to length, a Phil Wood machine was over $3K last I knew. 

It seems to me your biggest hurdle is getting a wholesale account.  Most distributors want
to see a picture of a brick and mortar storefront and some credential and or web-presence.

We use J&B importers for our "bread and butter" supplies, but also have accounts with QPB and
recently Shimano.

Yeah, wheels are the Achilles' heal of used bikes, especially rears.  I usually start any wheel work
with hitting each nipple with Tri-flow.  It also helps to have an adjustable spoke wrench, often
an antique tool in my experience, although we have a Hozan, so they might be still available.  
We also has some spoke wrenches that grip three sides of the nipple, sort of, that work well
on stubborn spokes.  Hope this helps.

Mark Hoffman
New Britain, CT