Inclusionary zoning policy would ensure that new residential developments include a percentage of affordable units for people with low to moderate income.
While the best practice is for housing to remain affordable in perpetuity, many agreements for inclusionary zoning are for 10-25 years, and mortgages for co-ops and social housing have 30 year mortgages. When these contracts end, the affordability of these housing units can easily be lost.
This is why building or acquiring rental housing with the intention of perpetual affordability is so important. Partnerships with non-profit housing providers and community land trusts can make a big difference.