Your home must qualify as principal place of business (even if it doesn't qualify for deduction). (money.stackexchange.com)
The example you cite re first client being considered as the place of business is for the case where your home doesn't qualify as principal place of business. (money.stackexchange.com)
But that criterion is also mentioned in that publication as if it were separate from the «principal place of business». (money.stackexchange.com)