Each week the NZ Herald and Newstalk ZB's Cooking The Books podcast tackles a different money problem. Today, it's the third episode of our OneRoof-partnered series, looking at the tricks to negotiating a mortgage which could save you thousands. Hosted by Frances Cook.

Saving up for a house is one thing, but then actually paying it off is entirely another.

A mortgage interest rate may look small, with some rates currently under 4 per cent.

That's an incredible deal, but there's a reason the banks are willing to give it to you.

Over the course of a 30-year mortgage, that 4 per cent interest rate adds up several times over.

In fact, by the time you take into account changes in interest rates over that time, the general rule of thumb is that you pay double for your house – once for the purchase price, and then the same amount again in interest payments to the bank.

So you want to be smart about this from the beginning, because it means a difference of literally tens of thousands of dollars, maybe more.

Happily there's more than one trick you can keep up your sleeve to make sure you end up on the right side of the deal.

For the latest Cooking the Books podcast I talked to Ashley Church from OneRoof and Lesley Harris from the First Home Buyers Club.

We discussed whether you should use a mortgage broker, how to find the best rate and how to plan ahead for how interest rates could change in the future.

If you have a question about this podcast, or question you'd like answered in the next one, come and talk to me about it. I'm on Facebook here https://www.facebook.com/FrancesCookJournalist/ Instagram here https://www.instagram.com/francescooknz/ and Twitter here https://twitter.com/FrancesCook

If you missed the previous episodes, go back in the episode list to listen to how life stage impacts renting vs buying, and an interview on ways to save a house deposit on an average income.