Generally you would set the minimum number of days for the job at hand, build in some breathing room, head scratching room and often end up at 3 weeks work for something that in ideal perfect circumstances with no code issues or error, take 5 days.
So per day billing is not just silly, its impractical as well from the business standpoint, NO ONE in business will pay for services like that, ask anyone who has to pay for something and it has to have its on table in a ledger... lot of work.
So it is more realistic to raise an invoice for payment at regular intervals like weekly if you want weekly or at the end of the month or on completion of the job or in some cases, on customer satisfaction that their request for a product works.
Whatever mode you chose, in the world of business it will not be daily billing.
@bradvictor1Jan 17.2019 — #work with module wise and charge accordingly. If client want pay to on daily basis then charges would be depend on hours which you will work for him or her.