I dont necessary support the Arthur Murray philosophy but in Dance-sport we have an Associate Coach who works under the guidance of a professional. To be an associate coach you have to do tests in the three styles on offer in Australia. I would not support someone who has no dance training at all . But to be taught by the associate teacher will give a lower cost for someone coming into dancing. Bad habits should not take a lifetime to leave the brain with clear instructions.
I think that usually its near disasterous. Lessons from someone that can not really dance can set you back rather than put you forward - and may well be harmful to your body. The whole point of dancesport is that it mazimizes what two people can do together dancing while minimizing risk.
If I were starting again and knew what I do now I would not go ANYWHERE NEAR such incompetent coaches. Why do that when for a few dollars more you can get real training from real pros.