My wife (God bless her)lets me think i'm fooling her.You will be selling existing gear to fund this new gear, hence "no cost at all"?
In all honesty though, I've stopped the excuses with the Mrs because they always find out... ALWAYS!
So now I've just put on my big boy pants and disclosed vaping as my hobby and set aside a hobby budget. Saves me from spending too much and I don't need to come up with a story when I need to buy things.