The first rule in housing is don’t lose what you already have. Retain smaller, older cottages, duplexes and even multi-unit buildings. Rehabilitate, don’t destroy.

Not only are older structures part of our community’s history, but they also tend to be the home of our workforce and the elderly. They are also more properly scaled for small- to medium-sized towns than the behemoths that might replace them.

Community land trusts embrace that approach along with funding and managing new housing.

The key idea is that a nonprofit is formed to purchase property, often with multifamily apartments already erected. Then they are converted to an ownership model where the land is owned by the trust in perpetuity. The apartments or even duplexes and single-family cottages are leased to low- and moderate-income people who have shared equity in their individual units.

It’s a nondisruptive route toward the “affordable” housing that each of Marin’s 11 municipalities and county governments are mandated to provide by the state.

Instead of building new blockbuster high-rise housing, use the land-trust model by acquiring existing structures that are then priced for low- and mid-income families.

Some can be as small as two units.

Consider Fairfax, where 243 units of housing are proposed for a six-story apartment complex at 95 Broadway. Of those, only 42 are “affordable.” That component could be addressed by a community land trust purchasing existing multi-unit market-rate housing. Then, reposition the units to apartments for those who are income-qualified for shared equity ownership.

The land-trust scheme has been around since the 1930s. There are now 225 land trusts in the U.S. The largest is near Burlington, Vermont, adjacent to Lake Champlain.

As the Vermont trust explains, “The real innovation of the program is that the Champlain Housing Trust and our buyers agree together to preserve affordability forever by sharing a portion of the home’s appreciation at resale.” So far, the Champlain trust has made 679 homes affordable for 1,320 owners.

Mt. Tam Land Trust was formed with similar intentions. Its primary goal is to purchase multi-unit parcels with housing already built. Then the land is permanently owned pursuant to what lawyers call a ground lease.

The apartments are then sold using the shared equity model. Prices are set so that they are affordable for first responders, teachers, those working in service and retail industries, our older citizens and the physically challenged population.

It’s not a new idea in Marin. The Community Land Trust of West Marin (CLAM) and the Bolinas Community Land Trust are already in operation.

Among its many accomplishments, the latter created Bo Linda Vista, an outlay of 60 small mobile units serving as emergency housing for displaced farmworkers.

CLAM owns 18 affordable rental units in Point Reyes Station, Bolinas and Stinson Beach. Meanwhile, the Homestead Valley Land Trust in unincorporated Mill Valley concentrates on purchasing land for open spaces.

Shared equity is already part of Marin’s housing matrix. Often a property owner is required to build a handful of “affordable units” to win approval to construct market-rate housing. Tenants have some equity that can be cashed out upon sale.

Unlike in the private sector model, with land trusts there is no possibility that (for 90 years from its establishment) the real estate or the units will be on the open market.

For Mt. Tam Land Trust, funding to purchase appropriate properties is priority one.

Mill Valley officials, with a push from Mayor Stephen Burke, are taking the next step. The City Council unanimously approved a resolution allowing Mt. Tam Land Trust to be a partial beneficiary of the city’s $1.5 million Affordable Housing Trust Fund. The fund derives from a 1% fee on residential building permits valued over $145,000.

Mill Valley’s action is a message to other Marin cities, towns and county governments that they need to financially assist the land trust to achieve its goals.

Columnist Dick Spotswood of Mill Valley writes on local issues Sundays and Wednesdays. Email him at spotswood@comcast.net.