The following is an excerpt from Mortgage-Free!: Innovative Strategies for Debt-Free Home Ownership by Rob Roy . One of the most popular and successful strategies open to you is to build a small, affordable core—typically in the 500- to 700-square-foot range—and then to build affordable additions as they become truly necessary. Several of our neighbors on The Hill have employed this strategy successfully. Sometimes the temporary shelter will serve as the core for the completed house, either by plan or by evolution. However, get one part of the house completely finished before moving on to the next part. Living in a house under construction puts tremendous strain on a relationship. If you can retreat to a clean and uncluttered living area, this “refuge” may prove invaluable on all living fronts. There are two schools of thought with regard to add-on houses. One is to have some specific expansion plan in mind at the initial design stage. The other says to let the house grow organically as such needs arise. My observation is that both plans will work, and therefore you should tailor your strategy to your personality. If you have an organized, analytical mind, you may be happier knowing that you’re working toward some specific end or goal, while a more spontaneous individual might feel cramped by such a plan, preferring creative freedom throughout. My own approach is a kind of hybrid of these two ideas. I allow myself to be locked into certain structural requirements, largely because I lean toward the use of massive timber-framing, cordwood masonry, and heavy earth roofs, but I give my spontaneous creativity its outlet by using special design features within the structural framework. Rather than feeling restricted, the use of stone and wood masonry gives me the freedom to create special textures, alcoves, and designs. Although I have not used the add-on strategy myself, I offer one strong caution, and it may be that my not using the strategy is a direct result of not having been so cautioned myself. All four houses that Jaki and I have built would be quite difficult to add on to, both structurally and aesthetically. They were all designed to be complete in themselves, and therefore no thought was given to expansion potential. When Log End Cottage became too small, thanks to a small new member to the family, we had two choices: attempt a difficult addition or build a new house. Our decision was influenced by other factors, especially a desire to greatly reduce our firewood requirements and my new interest in earth sheltering. We decided on the new house option. Not always one to learn from my first mistakes, I went and designed Log End Cave—also without expansion potential. In fact, the Cave was even more locked in to its size and shape than the Cottage! While it is true that the Cave’s 910 square feet of useful living area is quite sufficient for a young family of three or four, it is a little disappointing to know that this size is pretty much what one is stuck with. Small is beautiful, yes, but have a care for the future. If you’re planning an earth shelter, be aware that, unless expansion is specifically addressed at the design stage, it is very difficult to add on to an underground house. A young couple with several small children once visited us to discuss earth-sheltered housing. They insisted that they absolutely had to have 1,600 square feet of living area, minimum. The trouble was that they could only afford 800 square feet. I advised them—I always give better advice than I take—to build the 800 square feet that they could afford, leaving the east wall of concrete block externally insulated, but not backfilled. Because they were both making good money as truck drivers, they could afford to complete the other 800-square-foot module two or three years down the road. This could be accomplished by reusing the rigid foam insulation (possible if it is protected from the sun’s ultraviolet rays) and using the internal masonry wall as a thermal flywheel and effective noise buffer between one side of the house and the other. The result: an energy-efficient, debt-free home. The trade-off: two or three years of less than the desired living space. I have heard of people using the add-on strategy to get around building permit problems. In New York, for example, any house over 1,500 square feet requires an architect or engineer to stamp the plans that are a part of the permit application. Here, building the house in increments can save a lot of money in professional fees. I’ve also heard of municipalities that have come up with creative ways to discourage or even prohibit the add-on strategy, so be wary. Sometimes zoning regulations will stipulate a minimum house size, maybe 2,000 square feet or more in posh neighborhoods, to “protect the property values in the neighborhood.” The reader will have a pretty good idea by now of how I feel about such regulations. Taxes are based on valuations, and valuations are based on square footage first and foremost. So such regulations could be seen as rather self-serving on the part of the municipality.