Using box spreads to finance life?
So I've been planning to move back to the US in the next 12 months - and was looking at buying a house, and also tax planning/withdraw strategies (I fired 18 months ago). I happen to come across box spreads (european SPY box spreads) as a way to effectively borrow money at near SOFR, while also offering short/long term capital loss for the 'interest' paid.
That got me thinking - with my now almost $12M in assets (80% VTI/SPY/QQQ and 10% old legacy vested RSUs that I'm planning to sell after I move back to the US for tax reasons, 10% SGOV), if I fund my full expenses with dividends and box spreads (I'd have about $100k in dividends + take out $150k/yr with box spreads) and roll it over every year - I'd still be able to keep my debt-to-asset ratio at less than 20% basically until I die. And thereby pay minimal taxes forever.
Is that right/sound? What am I missing?
I know there is risk if markets drop 80% or what not, or if VTI growth slows dramatically over the next 40 years, or if interest rates spike dramatically to the 1970s levels, etc - but all of those seem like tail risks that either means I'm screwed either way (if the trigger/shock event happens suddenly and is sustained - like WW3), or I'll be able to modify behavior to de-risk (reduce spend, stop rolling over the box spreads, etc)