Reasonable minds can disagree on how much affordable housing is appropriate for Santa Monica, and whether rents, kept at affordable rates by rent control, should be counted in determining whether Santa Monica has adequate affordable housing. But assuming that Santa Monica needs more affordable housing, acquiring that housing should be done in a cost-efficient manner.
Currently city staff is focusing on new development being the primary source of new affordable housing (i.e. producing this housing on the most expensive land, in the most expensive buildings). Using this method, the cost of each affordable housing unit is astronomical. A dramatically better solution would be purchase, deed restrict, and then sell existing apartment buildings.
First, have the developers contribute what would be the real cost of providing affordable housing in their new buildings, and then put that money into a fund to acquire affordable housing. Purchase older apartment buildings, which have a large percentage of units that are rent controlled at a fraction of market value. The city could then immediately lower the rents for qualifying tenants to affordable levels; and as units naturally turn over, lease those units to qualifying tenants, at affordable rents.
Over time, the entire building will have qualified tenants at affordable rents. With some patience the city would maximize affordable housing. This type of plan would have the added benefit that new developments would not need to be so big, because the extra size for the affordable housing would not be needed.