The ability to sustain repayments on a mortgage can change rapidly. There are many home owners who have secured properties during the past few years who are now facing the prospect of losing their homes because they can't keep up with their monthly mortgage repayments.

Property affordability has dropped considerably in the last few months as interest rates rise and lending criteria tightens. While it is easy to use hindsight to see that many home owners who are facing the prospect of losing their home should not have leapt onto the property ladder in the first place, it is more sensible to focus on the issues that they should have considered before applying for a large mortgage.

When assessing whether or not to buy a property, a prospective borrower should first look at whether or not the mortgage they wish to apply for is simply too big. It sounds so simple – and that's because it is. Mortgage lenders offer products with income multipliers of more than five times an applicant's salary these days which is more than twice as much as it used to be.

This raises the question – why the increase? Twenty years ago lenders assessed that borrowers could only afford a mortgage of about two to three times their annual wage. Why are they now suggesting that borrowers can sustain a mortgage of five times their salary?

Even if a borrower secures a mortgage that they can afford at present, potential future changes in the terms and conditions attached to the mortgage and potential changes to the household budget should be accounted for.

The most obvious factor that can, and probably will, change is the mortgage's interest rate. When interest rates increase, monthly repayments on variable rate mortgages also increase. When fixed interest rate periods expire, the interest rate payable on a fixed rate mortgage may also increase. Both of these scenarios will result in an increase in the monthly repayment amount due on the mortgage and will therefore lower its affordability.

Finally, borrowers should factor in the possibility that their income may reduce. Any reduction in a household's income will naturally lead to the mortgage, as well as other bills, becoming less affordable. There are various insurances available to mitigate reductions in income and borrowers should research this carefully when applying for a mortgage.

Borrowers who plan ahead and factor in potential changes in the variables detailed above will have a much better chance of funding their mortgage through the bad times and therefore holding on to their home.

Before buying a home or remortgaging to a new home loan it is wise to speak to an independent financial adviser or mortgage broker to ensure that the most appropriate financial products are obtained. Financial information should be sought from an independent adviser to ensure the best advice possible is received.