btw there are TONS of yoga instructors out there now. Studios love running teacher training because it is a big money maker. So you should find, particularly if you offer pay that is industry standard for your geographic area, that you have no problem getting a wide choice of teachers. One suggestion I would make is to visit a few stand alone yoga studios in your area. Generally speaking these places will have some of the most experienced and most highly trained teachers. Try a few styles to get a sense of what would work for your clientele. You might also make some connections to the yoga population as a whole that way. Then when you have an opening you could say, for instance, ‘I want someone with experience teaching warm vinyasa/multilevel yoga/chair yoga/Bikram/Viniyoga/Iyengar or whatever you need.
As an aside, the Yoga Alliance just sent out its summary of its recent yoga study, done in conjunction with the Yoga Journal. For every yoga instructor that’s out there now, there are 3 in yoga teacher training.
As yoga is growing in popularity, so is the supply of yoga teachers. You likely have lots of people to pick from should your original candidate with the NESTA certification not work out.
Although the Yoga alliance is nice, it is not a requirement, and will not determine if a Yoga instructor is skilled, and competent. Moreover, the more experience one has, the better they are able to lead others in the right direction safely. If an individuals has many years of experienced in athletics, and yoga in general, an online program is a good edition to add.