Some things that could make a person a poor candidate for homebirth:
liver or kidney disease
Bleeding and clotting disorders
unresolved seizure disorders
use of drugs and alcohol
untreated mental health issues (and sometimes even with treatment they may be too severe to be a good candidate)
super complicated obstetric history that seems likely to repeat
being in overall poor health
There are likely other conditions that may come into play based on location (and things that I am likely just not thinking of at the moment). In some states midwives are unable to attend VBACs, for instance.
Type of twins and type of breech matters. Other factors with those things that need to be considered: what number baby is it? What is the gestational age? Do the parents understand what the increased risks are? Exact positioning. Distance from hospital. Local political environment. Experience of attendant. Size of baby (or babies in the case of twins). So, a midwife may attend a breech for one woman and yet transport the next based on all those things and how they make up the overall picture.