  We show how few-particle Green's functions can be calculated efficiently for
models with nearest-neighbor hopping, for infinite lattices in any dimension.
As an example, for one dimensional spinless fermions with both nearest-neighbor
and second nearest-neighbor interactions, we investigate the ground states for
up to 5 fermions. This allows us not only to find the stability region of
various bound complexes, but also to infer the phase diagram at small but
finite concentrations.
