Back in 2005 when liar loans were allowing everybody to buy into the skyrocketing housing market regardless of their ability to comfortably pay a mortgage a group of disgruntled residents in the Heritage Ranch neighborhood by Joshua Cowell School were furious.

It seemed one of the owners of the behemoth McMansions found in the neighborhood — giant rectangle boxes that are 4,336 square feet making them the largest tract homes ever built in Manteca — had five distinct households residing in it.

Neighbors weren’t ticked about noise but the sheer number of vehicles and people. There was a young family, a couple of couples, and single folks renting the seven bedrooms and sharing the kitchen and living area as common space.

The neighbors appeared at a Manteca City Council meeting indignant about what was happening as they had bought in a “single family neighborhood.” They demanded the city do something about it.

They were none too happy when they were delivered a dose of reality. Under court rulings and federal law cities could not ban more than one family from living in a so-called “single family house”. The term “so-called” is appropriate because long before 16 years ago the federal government demonized the term “single family” as the concept promoted housing discrimination.

Besides it is not illegal to rent rooms in your home to non-relatives.

At the same time another trend was taking hold — multiple families buying large tract homes and securing mortgages jointly. It effectively took new 3,800-square-foot tract homes fetching almost $600,000 in parts of Lathrop and Manteca down to a more affordable $300,000.

A small but solid number of new homes are sold each year in Manteca to multiple households that can’t be discriminated against applying for mortgages if they have adequate combined qualifying incomes. At the same time there are people — either young couples or single folks — who buy a new tract home and almost immediately post on various social media sites that they have rooms to rent.

None of this is illegal. And to be honest it is happening in neighborhoods across the state. How else do you think we can have a housing shortage of 3 million units as state leaders estimate and not have a million or more people living in the streets?

What is essentially “shadow housing” may soon come out into the light. And the odds are it won’t make very many people happy.

The McMansion next door could essentially be transformed into four housing units before you know it.

It’s because the move to kill off single family zoning in California as a way to solve the housing crisis is starting to get traction.

The Sacramento City Council on Tuesday voted unanimously to move forward with a draft zone plan that would allow anyone — but most likely investors — to either remodel existing “single family homes” or tear them down and start anew to create up to four separate housing units.

The Sacramento plan — if it eventually becomes law — would in about two years’ time allow anyone owning a parcel now zoned for single family homes to turn it into multiple family housing.

The plan as outlined would limit how much of a lot could be covered with a housing footprint. It also would limit the height to essentially what is already allowed in a neighborhood.

A similar measure failed last year in the California Legislature to require cities throughout the state to allow the same thing. The bill’s sponsor, State Senator Scott Weiner of San Francisco, has vowed to take another run at it during the new legislative session.

If you don’t think if such a law gets passed in California that it won’t lead to a rush of investors to buy “single family homes” and either convert them or tear them down and start from scratch to build up to four housing units you are in some serious denial.

An investor could buy a 40-year-old 1,400-square-foot home in a decent Valley neighborhood for $410,000. Based on comparable rents, they could command $1,900 a month in rent. Tear it down and build a two-story 2,800-square-foot replacement structure with three units each consisting of 933 square feet and they could rent each for $1,500 a month based on what a two-bedroom, one bathroom apartment with 725 square feet is now going for in many Valley cities. That is $4,500 a month versus $1,900 a month.

Of course, a catastrophic housing market correction — 2008 is the best example but 1991 wasn’t far behind — that seems to happen every 15 years or so and it’s off to the races.

Those gigantic McMansions just shy of 4,400-square feet in the last housing correction plummeted from a high sales mark of $750,000 down to a low of $225,000.

Almost all that went into foreclosure were snapped up by out-of-state investment firms. That’s because when most people finally felt comfortable buying homes they intended to occupy again there was plenty of smaller yet still good-sized foreclosed homes out there that were even more affordable. And they didn’t have as big ongoing costs for heating and cooling as also as general upkeep and maintenance.

Should an event like 2008 happen again and the state enacts a law such as Sacramento is now considering that would apply to all California cities, rest assured most foreclosed McMansions in excess of 4,000 square feet will be snapped up by people eager to quadruple down on their investments.

Many of the Heritage Ranch McMansions built by Seeno Homes offer a head start with a second flood in-law suite complete with kitchenette and second floor master suite with more almost 1,200 square feet that would make it a breeze to convert.

You may think this sounds far-fetched but the demand and return are too good for a savvy investor to ignore.

Toss in the trend of large corporations backed with more cash than what circulates in all for Third World country, and you could see a fairly rapid transformation.

It would no longer be perhaps just under 8 percent of all traditional single family homes housing two households defined as couples, a family or single individuals. Based on the fact at one point or another 15 percent of Manteca’s housing stock the last time around was in forecloses or short sales, the number of homes with multiple families could easily double based on separate parcels but triple or quadruple based on potential housing units.

The neighborhoods of “The Brady Bunch” and even “Ozzie and Harriett” could indeed be numbered.