Complex sentence: Beginning in the 1990s, older housing stock has been joined by loft-style condominiums, many of which were built under the cover of "live-work" development ostensibly meant to maintain a studio arts community in San Francisco.
Split into simpler sentences: Beginning in the 1990s, older housing stock has been joined by loft-style condominiums. Many of these were built under the cover of "live-work" development ostensibly meant to maintain a studio arts community in San Francisco.