One in five mortgage holders would be forced to make spending cutbacks if interest rates started rising - and one in 14 would seriously struggle to cope - a report has found.
Half of people surveyed for Nationwide Mortgages said they were already using credit cards and overdrafts to fund their everyday spending, including food bills.
If rates moved at all, 20% said they would have to cut back on spending and a further 7% believed it would leave them seriously struggling.
Nearly one in five (18%) of the 2,000 homeowners with mortgages surveyed had no rainy day fund to call on in case of emergencies.
The research was released after the Bank of England last week marked seven years of the base rate being held at its ultra-low 0.5% level with another decision to keep the cost of borrowing on hold once again.
Mortgage rates have fallen to record lows while the base rate has remained at 0.5%, keeping borrowing costs relatively cheap for home owners.
Any increase in the base rate would be a new experience for more than two million first-time buyers, who have climbed on to the property ladder while borrowing rates have been generally falling or static.
The research also found that 16% of people were more interested in talking about the weather than interest rates. One in 10 said they did not know how interest rates worked and were not interested in finding out.
While 39% of those surveyed had used the relatively cheap cost of borrowing from low interest rates to overpay their mortgages and repay their debts, 6% had used the opportunity of having more cash in their pocket to spend.
Homeowners in East Anglia and the South East of England were most likely to have used low interest rates to make regular overpayments to their mortgage.
Those in the West Midlands and Northern Ireland were the most likely to have spent any extra cash, with 10% having done so.
Nearly a third (31%) of homeowners had never checked if they could save more money by switching mortgage provider.
Several mortgage price wars have broken out recently. In a more recent twist, the number of lenders offering "sweeteners" such as cashback and free legal fees has increased sharply.
According to financial website Moneyfacts.co.uk, three-quarters of mortgage deals on the market offer borrowers some form of incentive, up from 62% a year ago.
Here are some tips from Nationwide Mortgages, part of Nationwide Building Society, for getting on top of your finances:
:: Write a list of income and outgoings, including all bills. Decide whether you can make any reductions to free up more cash
:: Check the terms of existing arrangements such as any mortgage, loans and savings to see if you can improve them or get a better deal elsewhere. While rates are low, consider whether you can overpay on regular debt, like your mortgage, to reduce the size of your debt and give you greater options in the future
:: Plan your priorities. Pay off expensive debt first and where the terms and your budget allow, pay off debts as quickly as you can. Build up an accessible rainy day fund - ideally enough to cover a few months' bills. Start specific savings pots for particular life events