"The question of ‘How are you going to pay for it?’ is now perennially used by journalists to challenge any proposal made by any politician on any issue, whatever its inherent merits might be.....

That correct answer is ‘We’re going to work for it.’ After all, how else is anything paid for? When the government has a plan to spend money it intends to put people to work. And to answer the question ‘How is it going to be paid for?’ the correct answer is ‘From out of the value created, which is why we’re doing it."
http://www.taxresearch.org.uk/Blog/2018/07/24/the-right-answer-to-how-are-you-going-to-pay-for-it/