User blog comment:Space-churro/How do I become vocaloid/@comment-32500188-20140529050900

Well... there's a stark contrast between the creation of an UTAU voice bank and the creation of a VOCALOID library, mainly that of license fees, production costs, and a whole lot of other legalities/complicated processes that you have a very slim chance of running into if you stick with the first one of the two. XD

This presentation that VoxWave gave back in March will give you a brief summary of what the gameplan of Vocaloid production is like... although it varies between different companies, a majority of the process is the same in terms of having the funding and getting the green-light from Yamaha in order to be able to start production. (make sure you have captions turned on for subtitles.)

PlantyP also has started a podcast series related to Vocaloid info, and his first Vocaster post goes into a good amount of detail with how a Vocaloid voice library is made.