"rank beginner" wrote in message
Well, what if you don't have even a circular saw? I can't afford one
at this very moment, nonetheless need to
get building now, because I have other projects that need to get done
which themselves require a proper bench with vises. So I need to know
whether its feasible for me, someone just starting out (but with
mechanical aptitude), to attempt to use a regular hand saw for doing
the cross cuts on the construction-grade lumber (or maybe clear
hardwood, haven't decided yet).

Sure, why not? They build some rather nice furniture before the invention
of electricity and power tools. If, however, you have to buy a handsaw, you
can buy a circular saw for less than a good handsaw.

Take your time and mark a line for the cuts.