The 1987 United Nations Brundtland Report established the vision of sustainable development as "development that meets the needs of the present without compromising the ability of future generations to meet their own needs." How might we anticipate the requirements of future custodians of vast, continuously morphing socio-technical-ecological systems while addressing current pressing needs? An abstract, principled approach (such as axiomatic design) might help address such ambiguity. Such systems are composed of large numbers of information-processing agents/agencies that collectively form a complex adaptive system (CAS). The focus here is on financial sustainability: (1) what is a principled approach toward sustainable design? (2) What design insights might we obtain by studying financial crises forensically against sustainability successes in nature? (3) How to design for financial sustainability? This paper adopts the CAS framework alongside axiomatic design to help elicit design patterns and anti-patterns of sustainability. Inspired by nature, a promising inside-out design pattern emerges.