The mortgage REIT offers a prodigious dividend yield.AGNC Investment (AGNC -1.82%) currently offers a monster dividend yield. The mortgage-focused real estate investment trust (REIT) has a payout approaching 14%. That's more than 10 times higher than the S&P 500's dividend yield. Here's a look at how much you'd need to invest in the high-yielding mortgage REIT to collect $1,000 of dividend income each year.AGNC Investment pays a monthly dividend of $0.12 per share ($1.44 annually). At that rate, you'd need ...