If property owners have the option to convert single family homes into duplexes, they can do that. Then if there's not enough demand for their units, they lower

If property owners have the option to convert single family homes into duplexes, they can do that. Then if there's not enough demand for their units, they lower the rent until they fill the units. If demand is really high, then more property owners will start converting. If demand remains high, eventually those duplexes will be cleared out for some modest apartment complexes. For areas that don't have a lot of economic activity, I think very few homeowners will go through the expense of converting their properties because they won't be able to make the money back on rent. In those areas it would be more efficient to build new SFHs on vacant lots. Either way, with byzantine zoning rules out of the picture, the pricing and incentives to build, sell, or rent will match the local area much better.