Alyse Nelson writes that when it comes to houses, bigger isn't always better:
My husband and I think we’ve found a way to pay off our mortgage early, without taking on an extra job or working nights. We’ve decided to construct a rental unit — a “mother-in-law suite” — within our home. If it pans out as we hope, the rental income will let us pay off our loan 10 years early. And who knows: It could give us a chance to live closer to family as we, or they, get on in years.
Jason and I are not alone; lots of folks across the country are experimenting with adding a second (or third) dwelling to an existing single-family home. And in perhaps the most interesting development, more and more people are choosing to buck the “bigger is better” trend in North American housing. They’re taking small spaces — backyards, side lots, or freestanding garages — and using them to build tiny houses.
What's left out of this discussion, however, is that this isn't just a question of taste. It's a question of law. In Washington, DC for example accessory dwellings are currently illegal in all the areas marked yellow, orange, or red on this map. The Office of Planning is proposing to change that, but it's fairly controversial. Montgomery County in the suburbs recently relaxed its rules against accessory dwellings but they're still pretty strict, limited "to one per house, with no two apartments being within 300 feet of one another" and each "apartment would need to have its own parking space -- two if the main house does not have a driveway."
And I think you'll find that this is quite frequently the case all across America. It's a shame since the demographics of the country have changed quite a bit. Compared to 50 or 100 years ago, a much larger share of Americans are either childless or empty nesters. Families that do have kids have fewer kids on average. There are more single people. Under the circumstances, it's extremely sensible to re-purpose certain kinds of older structures as multiple dwellings. But the prevailing legal climate in most places is fairly hostile to this.