If you're building a mammoth development in San Francisco like the one proposed by Maximus Real Estate Partners for 330-ish apartments at 16th and Mission, there are a couple of rules. You're required to build 20 percent affordable housing off-site, or to build 12 percent affordable housing on-site, or to pay a serious fee — and under Prop K, passed in November, that overall number pushes to 33 percent.

The current plan (renderings and details here) for 1979 Mission Street have been called by opposition like the Plaza 16 Coalition "the monster in the Mission." But developers are hoping to quell such vocal detractors by giving the project a turn of the screw, now proposing twice as much below-market-rate housing.

Though they had previously pledged the minimum 12 percent affordable rentals, as The Business Times reports, Maximus Real Estate Partners is now calling for 24 percent of the project's total units to be affordable. Here's the breakdown:

• 290 market-rate apartments on-site.
  
• 41 "middle-class" for-sale units on-site for $280,000 to $350,000, sold to households making between $61,000 and $145,650.
  
• 49 below-market-rate rentals built off-site at a TBD property in the Mission, priced as affordable for those earning 30 to 55 percent of the median income in the city.

Those on-site units for middle class buyers are to be sold at higher rates than mandated by law mandates for below-market-rate sales. Then the $12.3 million gained from their sale would go toward the construction of the off-site affordable rentals.

"We believe this plan provides a way for people at all income levels to live at 1979 Mission," Seth Mallen, who is the principal for the 1979 Mission project, said in a release.

Promises have also been made to improve the 16th and Mission BART plaza, in part by increasing its size by 40 percent. Also, a new playground for nearby Marshall Elementary School has been proposed, along with a "mercado" retail space for local artists and businesses plus the Walgreens currently on site.

To reach the voter-approved Proposition K goal — making one-third of the city's housing units affordable — there's plenty of work to be done, and perhaps creative steps like these are ones in the right direction. "This is going to come up again and again as far as the debate between progressives and moderates: How do we satisfy 33 percent?" Tim Colen, executive director of the Housing Action Coalition or SFHAC, told the Business Times. "It's very difficult without more funding, more height and a dial — otherwise you can't get to 33 percent. Maximus is saying, 'We're putting in the dial.'"

Tonight, Maximus holds a public forum for 6:30 p.m. at Laborers' Local, 261 Union Hall, 3721 18th Street. And afterward, the Plaza 16 Coalition has already planned its response, a rally and press conference.

Previously: Check Out These New Renderings Of The 16th And Mission Development