  We investigate the evolution of self-gravitating either dissipative or
non--dissipative systems satisfying the condition of minimal complexity, and
whose areal radius velocity is proportional to the areal radius
(quasi-homologous condition). Several exact analytical models are found under
the above mentioned conditions. Some of the presented models describe the
evolution of spherically symmetric dissipative fluid distributions whose center
is surrounded by a cavity. Some of them satisfy the Darmois conditions whereas
others present shells and must satisfy the Israel condition on either one or
both boundary surfaces. Prospective applications of some of these models to
astrophysical scenarios are discussed.
