IMHO, there's no way to get a 4% yield without a good amount of risk. Not that that isn't okay, just that one should be aware of the risks assumed. There are the most obvious ones - interest rate risk (loss of value due to increasing rates) and credit risk (delayed payments, defaults, loss of principal).
But there are some others as well embedded in several of the suggestions. One is declining value of your portfolio, not due to interest rate risk or even inflation (though that one's omnipresent). Rather it is using principal to get higher current yield.
If you buy a bond with above market interest (current yield, coupon), you'll be paying above face value (premium bond). For instance, you might pay $110 for a bond with a $100 face (par) value, you'll get that higher stream of payments, but you're gradually losing value, beyond inflation. Same thing with bond funds. This is why I prefer to look at SEC yield, which incorporates this loss (or gain) in bond value in calculating an effective yield.
PONDX's trailing yield is 7%+, but its SEC yield is 3.35%. Conversely, DVY's trailing yield is 3.09%, but its SEC yield is 3.46%.
Another risk is leverage. Funds, especially but not exclusively CEFs (e.g. PONDX also leverages), borrow money at short term rates to buy long term securities yielding more. This works so long as the long term securities continue to yield more. A risk is that rising interest rates will make replenishing cash more expensive (as the short term debt matures), and perhaps even cost more than the fund is receiving on its older long term securities.
Here's a M* video from 2013 (a few
years before short term rates started rising), that explains how these funds may work:
http://beta.morningstar.com/videos/610062/What-Will-Higher-Rates-Mean-for-Levered-Closed-End-Funds.htmlThen there's the use of derivatives. This can be anything as "simple" as mortgage backed securities (with call risk that can behave poorly with rising interest rates - negative convexity) to a slew of more esoteric stuff. In its analysis of DLTNX, M* lists some of these (while acknowledging that DLTNX has matured a bit): "These securities, which included inverse floater, interest-only, and inverse interest-only mortgage tranches, throw off lots of income but can also be highly volatile and suffer from bouts of illiquidity."
For the most part, you're seeing lots of fine suggestions here, and there's only a little I can add to them. I would not use BAB - Build America Bonds haven't been issued for
years. As a result, all the other funds (e.g. BABS [
Nuveen], BABZ [
PIMCO]) have closed down or broadened the types of bonds they can invest in.
If you're looking at SCHD and DVY, you might want also want to look at VYM. It invests a bit more broadly (~400 securities vs. ~100 for the others), with half the turnover (11% vs. 21-22%). Not significant differences, just another alternative to throw into the mix.
Finally, I'm still working on figuring out how PGBAX seems to walk on water - trailing and SEC yields of 5%+, no leverage. It does dive deeply into junk (averaging B rating), but the closest world bond I found so far, RBTRX, has a significantly longer duration and an SEC yield of "just" 4.5%. So credit rating alone isn't the full story.
If this type of portfolio appeals to you, you might also look at TTRZX or GIM. GIM has been trading at large discounts for the past three
years (perhaps reflecting its poor performance over that period, or perhaps its move to almost all EM bonds that typically trade at similar discounts).