You should not date the spouse of a client
Craig has met the wife of one of his biggest clients at his work.
Craig wants to see the woman again.
Craig invites his client and his wife to his home to meet his own family.
Craig invites his client's wife back to his house for drinks.
The client is impressed that Craig is a family man and sends more business to Craig.
The client stops doing business with Craig and Craig's business goes bankrupt.