Since we can't get parts nearly as cheaply as larger companies, even the common training sets like Ultegra/Open pro will cost you more to source and build than to buy pre-built, you might think about approaching this idea from a different direction.

If you really are very good at building wheels, and are looking for the opportunity to expand your experience base, you might try contacting some LBS's to see if you could strike a deal with them. They can bring the demand from within the store (customer's asking them about custom wheel options), they can do the sourcing of parts at wholesale pricing, but may not want to do the building themselves since it's a specific skill-set that most mechanics lack proficiency in. You may be able to work our a deal that will give you a fixed dollar amount ($30) or so per wheel build. They're happy because they can offer 'custom wheels' to customers, and you're happy because you're working on a wheel by wheel contract with no risk of loss.

At least that's what I would try if I could bring my per-wheel-build-time below 2 days

-Jeremy