The "Good Character" guidance for case workers (
https://assets.publishing.service.gov.u ... idance.pdf) has the following to say about debt:
Page 37/38:
Debt
An application will not normally be refused simply because the person is in debt,
especially if loan repayments have been made as agreed or if acceptable efforts are
being made to pay off accumulated debts.
However, where a person deliberately and recklessly builds up debts and there is no
evidence of a serious intention to pay them off, the application will normally be
refused.
Page 39:
Non-payment of council tax
An application will not normally be refused where the person has been unable to pay
council tax because of their financial position, particularly if an arrangement is being,
or has been, negotiated with the relevant authority. However, payment of council tax
is a legal requirement and non-compliance is a punishable offence.
Therefore, an application will normally be refused where a person has either:
• unreasonably failed to pay
• provided a false statement or statements, including failing to declare their full
circumstances, to avoid paying the correct rate
So with your debt history it seems you will have to show that repayment plans are in place and that you are complying with those plans or that you have completed the plans as applicable. Regarding rent, if you are taken to court this could lead to a CCJ which will be on your record as well. There is no rule on how long you should be paying off debt before applying - main question is are there arrangements in place and are you / have you complied with those. UKVI may ask for documentary evidence for this.
Another thing to consider: unless your debt position is under control a case worker might question why you are not putting the fees for naturalisation towards clearing your debt. This is just speculation on my part - but remember the "Good Character" requirement is not defined in law so UKVI might take a view.