Jesus uses this question to prove that people count the cost of a project before they begin it. AT: "If a person wanted to build a tower, he would certainly first sit down and determine if he had enough money to complete it" (See: [[rc://en/ta/man/translate/figs-rquestion]])
"when he has built a base" or "when he has completed the first part of the building"
# is not able to finish
It is understood that he was not able to finish because he did not have enough money. This could be stated. AT: "does not have enough money to be able to finish" (See: [[rc://en/ta/man/translate/figs-explicit]])