Dont retire owning shares as your income, speak to a financial adviser but they use bonds as its a scheduled repayment and is far more defined then stocks. Some stocks can be great like
RDSB for the first time since ww2 cut back its dividend, thats a heck of a record but generally its not advisable to rely on even SPY as an index for income. USA has a premium to it and SPY is about growth, etc., I'd rather say FTSE but I could be completely wrong on that and actually asia pacific is far better placed, nobody can say for sure but I'll throw out $2 million as your question answer or 2.5% (50/0.025)
https://seekingalpha.com/symbol/SPY/dividends/yield
That link says 1.92% average or $2.6mil