Talk to your accountant. There are some very good reasons to pay market rent anyway. Rental income is passive income and not taxed the same way as earned income. If the business is loosing money after paying market rent, you might be better off knowng that. You can also write losses off against other income of the same category. You can always loan the money back to the business without interest. If that creates a negative balance sheet and this a problem, you add the money back in as capital instead.
Also, if/when the time comes to sell either the business or the building, having a consistent arms length relationship between the two where the business pays market rent is beneficial. It helps to establish fair value for both entities.
Also, you have to take downside into account. If your business fails (unpleasant thought, but one you have to include in your considerations) and there is an accumulated loss you can write it off. If you never paid the rent, you will lose that portion of the writeoff.