From the Watchtower 15 August 1992 "Have You Counted the Cost?":
More
Than Common SenseThe wisest man who ever walked on earth, Jesus Christ, provided the guideline in one of his parables. "Who of you that wants to build a tower does not first sit down and calculate the expense, to see if he has enough to complete it?" Jesus asked. "Otherwise, he might lay its foundation but not be able to finish it, and all the onlookers might start to ridicule him, saying, ‘This man started to build but was not able to finish.’"—Luke 14:28-30.
Everyone would agree that it makes good sense to count the cost before deciding to do anything important. For example, if a person wanted to buy a house, would he rush into signing a contract without even finding out the cost and making sure he has the financial ability to complete the deal? He would be considered foolish indeed if he did such a thing. Yes, it is common sense to count the cost before one begins an undertaking.