Other than the Timex/Sinclairs, what's the
cheapest machine which was
 available in 1982 that I could have used to learn BASIC and assembler and
 machine code -- at home? 
The MicroACE.  Available in kit form for about $170, that included the
extra 1K of ram ;) for a total of 2K ram. Basic in rom, video modulator
on board, cassette interface. Basically looked like a timex/sinclair
though. I bought mine definitely before 1981, so probably in 79 or maybe 80.
-Lawrence LeMay