The Santa Ynez Band of Chumash Indians donated $20,000 to help underwrite construction costs for Habitat for Humanity’s 12-unit affordable townhouse project now underway at the corner of Canon Perdido and Milpas streets. When complete, those units will be occupied by families with incomes between $30,000-$60,000 a year. The price of the no-interest loans will be calibrated so that no one pays more than 35 percent of their income for housing. In exchange, the new owners — selected from more than 100 applicants — have agreed to put in 250 hours of “sweat equity” helping to build the new development. In addition, they take homeownership readiness classes and agree to keep no more than one car on-site. The project, slated for completion next summer, received nearly $1.5 million from City Hall’s redevelopment agency.