Supporters of a capital gains tax to cushion such wheeling and dealing might bristle at the unfairness of it all - giving some people a tax-free hand-out while others pay their dues.
But anyone with a reasonable understanding of tax law will know that, while New Zealand does not have an explicit capital gains tax regime, "speculators" or dealers - people who buy things with the intention of selling - must by law pay tax on the profit.
The couple in the Herald story seem clearly to fit that category and perhaps like all good citizens they will declare their bonanza and pay perhaps $70,000 or $75,000 in extra tax. But you'd have to wonder if that was the way it turned out.
The story - and many more like it over the last year or so - raises the question: through ignorance or simple cheating, how many New Zealanders are evading taxes and pocketing the profit on properties bought with the clear intention of selling on a rising market?
On the anecdotal evidence, the feeling is that Inland Revenue is missing many of the "players". In the two years to June 30, 2012, just 618 speculators showed their hands or were uncovered, leading to tax revenue of about $57m. In the 10 months to April 30 this year, a further 174 cases (involving $24m) were handled by IRD, and that had expanded to a total of 450 cases by the end of the June year. The "speculation revenue" for the last year hasn't been revealed, but may be around the $50m mark.
So we're talking here of around 1068 episodes across the last three years - and tax revenue of perhaps $110m - from a total of perhaps 220,000 national sales. Of those 1068 cases, around 25 per cent were candid when IRD raised questions and escaped a full audit, if figures for the last year are any guide. The remainder were probably less open and many may have argued their profits were not caught by tax law.
That $110m is a healthy little sum, but the suspicions are it could be much more impressive if people were more honest (or less ignorant) and if Inland Revenue was allocated greater muscle to track defaulters.
The overall figures suggest IRD may be just scratching the surface, especially in times (like now in Auckland) where house sale volumes are returning to levels reached at the height of the boom years.
Those sorts of volumes, coupled with the endless faith of New Zealanders in the investment power and security of residential real estate, could be hiding hundreds of millions of dollars a year from the taxman.
Under tax law, "property investor" is a collective term for speculators, dealers and investors, and each is treated very differently.
IRD says three main factors can determine status as a property buyer for tax purposes: the intention when buying a property, the patterns of previous property transactions and association with a builder, dealer or developer.
If you live in your home and sell it for a profit four or five years later, Inland Revenue will have no interest because the prime intention in buying was a roof over your head. But houses, flats or apartments that are not occupied by owners are in a different category.
Generally speaking, if you buy a property to use it to generate on-going rental income and without any firm intention of reselling, you are an investor. The property is a capital asset and any later profit or loss (after selling) isn't taxable.
However, if you buy a property always intending to sell it (whether it's one property or 20, and whether you rent it out or not), you are deemed to be a speculator and the profit or loss on sale is taxable.
And if you have established a regular pattern of buying and selling properties, you're regarded by IRD as a dealer (or trader) and the taxman will want his share of the profit.
The "buy-and-flick" operators - like, it seems, the couple featured in the June Herald story - will generally be regarded by the department as speculators and dealers.
Around 67 per cent of New Zealand homes are owner-occupied and, taking state houses out of the equation, perhaps 26 or 27 per cent are rented out by landlords.
If houses, flats and apartments change hands in the same proportion, it could suggest up towards 60,000 sales in the last three years were turned over by other than owner-occupiers - in other words, landlords, developers and speculators.
But that could over-state the position. Property churn is more vigorous among owner-occupiers, with some surveys suggesting owners change addresses every seven or eight years on average. Professional landlords and people who buy a second house as a renter tend to hold their properties for the long term.
So, the "non-owner-occupier" sales of the last three years may be more like 45,000 or 50,000.
Even with that number, however, just 1000-odd cases of revealed or proved tax evasion seems very low. The suspicion is a lot of sales escape the IRD net, especially those manufactured by the tribe of "give-it-a-go" Kiwis who take their profit from one or two quick sales and keep it all to themselves. Professional developers, speculators and landlords with substantial interests can't fly so easily under the radar - not indefinitely anyhow - but how many are entirely candid with the taxman over property profits?
It's impossible to know how much potential tax revenue is going into a black hole, but it is certainly substantial. A clue can be found in this year's budget, which provided an extra $6.65m to chase property investment tax compliance. The expectation is it will return about $45m a year.
Inland Revenue's general reckoning is that the department will return in revenue five times the extra amount invested to investigate big-ticket areas such as property, the hidden economy and claimed losses. On that basis, an injection of $50m might produce an initial pay-off of something like $250m a year on residential property tax evasion - and, perhaps as the message got through, a better future rate of compliance.
Thomas Pippos, tax expert and Deloittes chief executive officer, says that given the amount invested in real estate the revenue now gathered by IRD could be "merely the tip of a bigger iceberg".
Asked if he thinks people are "having a go" in the knowledge they are unlikely to be caught, Pippos replies:
"I think that is probably fair".
He suspects many New Zealanders "near or across the boundary [requiring the payment of property tax] are either not aware of the boundary or assume optimistically that it is a boundary that is not in practice policed or acted on as potentially a justification for their inaction".
An Inland Revenue officer doesn't take much issue when it is suggested New Zealanders are not well educated over residential property tax liability and, even if they are, take their profit without declaring it.
"To an extent we agree," says the officer. "There are many myths about property in the public arena and some confusion over what is and is not capital profit."
Inland Revenue's own analysis shows the potential in targeting people who are revealed as likely traders or speculators.
A 2009 paper identified 2000 people who had bought and sold more than six properties over a four-year period; 312 of them were involved in more than 20 properties. The estimate was that extra tax of $214m could be owing - and the total would grow substantially if the 5000-plus other people who bought and sold three-to-five properties in the same period paid what they probably owed.
It's those sorts of figures, on top of the paltry existing 300 or 400 cases a year, that suggest hundreds of millions of dollars in evaded tax may be involved - even before the minor players are taken into account.
Because proof of intent at the time of buying a property is central to whether tax should be paid, liability is not clear without some investigation and resources are always best directed to areas where the potential return is greatest.
Investigators are more likely to be on the trail of dealers or speculators turning over several properties a year than the little guy who, over a lifetime, buys a couple of do-ups on rising markets and makes a nice little tax-free earner.
However, don't count on that so much in the future.
The department receives data on every property transaction in New Zealand and says that after a few years focusing on education and awareness, it is moving to "a targeted audit response" with "increased risk assessment and profiling of cases along with developing a range of tools including complex data-matching, analysis, research and evaluation".
And it adds: "By improving our approach and techniques regarding compliance, we are able to better identify those who may be deliberately breaking the rules."
It's taxman-speak for "be careful out there - we're watching and we may soon be knocking on your door".
