I already have most of this in the process of being taken care of and my GOD what a relief it is. Thankfully my godmother, uncle and cousin were all experienced backup singers and/or Broadway performers. I explained this situation to them and my godmother especially was like, “don’t you dare go wasting money on coaches when I’ll gladly help you for free!”Pretty sweet of her to respond.
If you're really serious about pursuing a career like that, you best start looking for a vocal coach and start taking music theory and solfege classes. I imagine sight-reading is going to be important as fuark if you're hired by a composer.