HARVARD -- With two potential projects in the pipeline, the Municipal Affordable Housing Trust, whose mission is to seek out opportunities to meet the town's state-mandated affordable housing benchmark, updated the selectmen Tuesday night on its progress toward that goal.

Beyond the numbers, MAHT Chairman Leo Blair said that overall, the group's aim is to control development under the Massachusetts "40-B" law, which allows developers whose proposed projects include a specific percentage of units deemed affordable by regional standards to bypass certain local zoning bylaws, such as minimum lot-sizes.

To that end, MAHT has entered into a pair of purchase and sales agreements with the owners of two properties it considers tailor made for its purposes.

Characterizing the two properties as "different" but both "appropriate," Blair said they are located at 361 Ayer Road and 166 Littleton Road, respectively. The 15-acre Ayer Road site was once slated for a market-rate housing development. The much larger property on Littleton Road is the site of the old poor farm, with frontage on two roads.

Blair said there's a long period of "due diligence" ahead, during which developers can submit proposals based on MAHT criteria that is now being worked out.

The group has separate visions for the two properties, with Ayer Road for family housing in detached and semi-detached, two and three-bedroom rental units. Being all rentals, the entire complex would count toward the town's affordable housing total, Blair said.

The Littleton Road property has three buildable lots on Pinnacle Road that can be carved out for single-family homes whose sale could subsidize lower-priced units, Blair said.

The main building, with 8,800 square-feet, would be suitable for condo units, with additional, attached units next door. Twenty-five of the units would be "affordable" and targeted to empty nesters, perhaps older town residents who want to downsize locally. MAHT member Chris Ready identified this need, Blair said.

Blair said a residential preference can be created for the affordable units, but not for the market-priced units, the potential buyers for which can only be preferenced by age limitations. Fifty-five or older, for example.

As for the market-rate, single-family homes, the "sweet spot" price range MAHT has in mind is "the low 300-thousands," Blair continued. And some of the "remarkably nice" property on Littleton Road would be preserved as open space, he said.

It's a "balanced approach," geared to meet the town's affordable housing goals without overwhelming it, Blair said.

If both deals go through, buildout for the two projects should take a couple of years on a staggered development schedule, Blair told the board. Tracing the chronology, he said requests for proposals would go out soon. The P&S agreements MAHT has in hand are transferable and the chosen developer can take it from there, he said.

MAHT's interest in pursuing these purchases now is stong because the price is right, he added, especially on the Ayer Road property, where the density would likely be much higher if it were sold to a developer privately.

Given the history of the Ayer Road property in particular, the selectmen suggested reaching out to neighbors as the process moves forward. The MAHT plans to do that, member Barbara Brady said. "Definitely we want to talk to people in the neighborhoods."