Some people could be tempted by gimmicks and inadvertently sign away tens of thousands of dollars refinancing their loan for a bit of extra cash, she said.
"You have to be very careful your loan isn't going back to a term that's longer than you've currently got. Banks always write a loan over 30 years, so if you refinance to another bank and you're 22 years into your home loan, make sure you keep it at the current loan term.
"If you go from a 22 to a 30-year term it could add $20,000 or $30,000 interest to the cost of your loan."
David Chaston of finance website interest.co.nz said the value of loan incentives depended on how they were used.
"If you're able to negotiate a good deal with the bank, ignoring the incentive, and then you add the incentive as a bonus you have a very good deal," he said.
"And you have an even better deal if you can use the cash incentives to pay down your loan."
Real Estate Institute head Helen O'Sullivan said an increase in marketing activity from banks usually coincided with the spring property uplift, but also warned consumers to be wary of temptation.
"You've got to weigh up the value of it with the overall package that is being offered ...
"Don't get blinded to the downside of the financial cost of something because of the excitement of getting a new PlayStation."
ASB's head of home lending and small business Vince Clark said the bank's spring package was in reaction to it being a typically busier season for house sales activity.
Kiwibank spokesman Bruce Thompson said its promotion was designed to keep the bank on mortgage shoppers' radars.
"It's a very competitive market and Kiwibank has never taken the approach of sitting back and waiting for the phone to ring."
ANZ head of mortgages Sarah Berry said the bank had offered cash with home lending since 2012 and the home loan market in New Zealand was very competitive.
Westpac said every customer's situation was different and the bank worked with them on a case-by-case basis to ensure they have the right solution for their circumstances.