This is just an example, funds can be used for any purpose. Including VAT, HMRC and other outstanding debts.
After 29 weeks this funding has been repaid and you repeat for the final batch of rooms.
After a total of 87 weeks you have upgraded and paid for all the rooms with no debt outstanding. Because the repayments were linked to card sales your repayments varied in line with your income so in your quite periods you could still afford the payments.