How about preferred stocks? You can fairly easily get a safe 7%.

Yes, you probably can, but you lose to inflation.
Assuming no change in market price of the preferred, both your real capital value and your real coupon value will erode at the rate of inflation.

Conversely, when you get a certain earnings yield from equities, it tends to be inflation adjusted on average over time.
If nominal earnings are rising at 5%/year in a 2% inflation environment, you can generally expect nominal earnings to rise at 7%/year in a 4%/year inflation environment.
To a first approximation, equity earnings yields are on average inflation adjusted: changes in inflation do not hurt your wealth.
That's assuming you are using a cyclical adjustment--obviously both earnings and prices do go up and down in the short term.

The exceptions are
* when inflation is so high that the economy breaks, but that's pretty rare.
* Some specific firms are unusually sensitive to inflation, and others are unusually resilient or even "antifragile". But on average it's a wash.

If there is any inflation over ~2% in future, a 5% earnings yield from a slate of equities is much more valuable than a 7% coupon from a fixed income instrument, whether bond or preferred.
Value Line currently covers around 240 stocks with P/E under 20, projected EPS growth rate over 10%/year, and projected annual total returns over 15%/year.
I would not put much faith in any of those numbers, but it seems not too hard to put together a broad portfolio with an earnings yield over 5%.
Your slate might not beat the broad market, but you'd be relatively immune from the risk of permanent capital loss from having a wildly overvalued portfolio--and the risk of inflation.

Jim