On Sun, 17 Nov 2019 22:14:03 +0000, Jake Chominsky
m wrote:

I have an 1950s home with older wiring. Most of the house only has a black
and white wire connecting to lights and recepticals. I want to do a 3-way
switch. Currently, the power is coming in through the light then connecting to
the on/off switch. How could I install a 3-way if I can only add a new wired
line from a new switch (#2) to the current light and also cannot upgrade or
touch the existing wired line from the current switch to the current the
current light? The reason I cannot touch the existing line is because it is
behind 2x4s and walls whered I have to demo a wall which is outside of my
capabilities.

I would look at a wireless solution. There is no way to add a 3 way
loop without running 3 wire plus ground cable.