Gavra:
I don’t think one can predict the future. It is just as (im)possible to support a family and pay tuitions on a Rabbe’s salary with a spouse’s income as it is if the husband were working in a typical white-collar office job. The additional income taxes, alone, are almost punitive.
Regardless, Parnassa, like everything else, is from Hashem, not from the profession you choose. I know many klei kodesh professionals who are managing just fine and, on the other hand, non-klei kodesh professionals including lawyers, who, unfortunately, are not doing all that well, financially.