I won't comment on your question re: paying down your mortgage or not - there are
calculators available that can help you determine if investing surplus income is prudent and a conversation with a registered Financial Advisor who knows you and your situation may be more appropriate.
The possibility of earning income from a security at a rate of 6% or greater certainly exists, but of course, none of them are without risk. You aren't likely to find a 6% CD these days and all short term, well rated bonds are yielding well south of 6%. The alternatives that do yield 6% and higher include Preferred Securities and Master Limited Partnerships. You can read a basic definition of Preferreds
here and a basic definition of MLP's
here.
Note that I am using the term "yield" while you used the expression "interest rate". It's a distinction that is important to keep in mind.
There are something like 1600 preferred securities that are publicly traded, and the overwhelming majority of the debt preferreds have a "par" or face value of $25.00. Some of them currently are trading at extraordinarily low levels with their yields being as high as 22% in some cases. As with any security, it is important to understand as much as you can about an investment before you buy, but just as an example of what is available these days, here is a list of but a few of the debt preferreds issued in 2008 offered by major financial firms;
Symbol & Security Coupon Moody's Effective S&P Effective Maturity EX- Next Equity
Description Rate Rating Date Rating Date Date Dividend Call Date Symbol
BB&T Capital Trust V 8.95% A1e 9/3/2008 A-e 9/03/2008 9/15/2063 11/25/2008 9/15/2013 BBT
JPM'I JP Morgan Chase 8.625% A1e 8/14/2008 A 8/15/2008 Perpetual 11/12/2008 9/01/2013 JPM
WCO Wells Fargo Capl XIV 8.625% Aa2e 8/12/2008 AA- 8/19/2008 9/14/2068 11/25/2008 9/15/2013 WFC
PHR Prudential Finan'l 9.00% Baa1 6/24/2008 A-e 6/24/2008 6/15/2038 8/27/2008 6/15/2013 PRU
CEG'A Constellat'n Enrgy 8.625% Baa2 8/20/2008 BB+ 8/13/2008 6/15/2063 9/10/2008 6/15/2013 CEG
IGK ING Groep 8.50% A1 6/10/2008 A 6/19/2008 Perpetual 8/27/2008 9/15/2013 ING
AZM Allianz 8.375% A3 6/03/2008 A+ 6/02/2008 Perpetual 8/27/2008 6/15/2013 ALVGR
BAC'H Bank of America 8.20% A1 5/22/2008 A+e 5/20/2008 Perpetual 7/11/2008 5/01/2013 BAC
FNM'T Fannie Mae 8.25% Baa3 8/22/2008 BBB- 8/26/2008 Perpetual 9/12/2008 5/20/2013 FNM
C'M Citigroup Inc. 8.5% A2 5/14/2008 A 5/23/2008 Perpetual 12/3/2008 6/15/2013 C
DKT Deutsche Bnk Capl TrV 8.0% Aa3 6/19/2008 A 8/01/2008 Perpetual 9/11/2008 6/30/2018 DB
FTB'C Fifth Third Bancorp 8.875% A1 6/18/2008 A- 9/03/2008 5/15/2068 8/12/2008 5/15/2013 FITB
RF'Z Regions Financial 8.875% A3 4/25/2008 BBB+ 4/30/2008 6/15/2078 9/11/2008 6/15/2013 RF
MER'Q Mer'l Lynch & Co 8.625% Baa1 7/17/2008 BBB+ 6/02/2008 Perpetual 8/13/2008 5/28/2013 MER
BCS'D Barclays Bank 8.125% Aa3 4/09/2008 A+ 5/19/2008 Perpetual 8/27/2008 6/15/2013 BACR
HCS HSBC 8.125% A1e 4/02/2008 A 4/08/2008 Perpetual 6/26/2008 4/15/2013 HBC
CRP Credit Suisse 7.90% Aa3 5/07/2008 A 3/25/2008 Perpetual 9/08/2008 3/28/2013 CSGN VX
AEP'A Amer'n Elec Pwr 8.75% Baa3 3/24/2008 BB+ 3/21/2008 3/01/2063 8/27/2008 3/01/2013 AEP
BWF Wells Fargo Cap XII 7.875% Aa2 3/05/2008 AA-e 3/05/2008 3/15/2068 9/10/2008 3/15/2013 WFC
CSB Colon'l BancGrp, 8.875% Baa3 2/27/2008 BBB- 2/27/2008 3/15/2038 11/28/2008 3/15/2013 CNB
KEY'F KeyCrp Cap'l Trst X 8.00% A3 2/20/2008 BBB 2/20/2008 3/15/2068 9/10/2008 3/15/2013 KEY
DRE'O Duke Realty Corp 8.375% Baa2 2/14/2008 BBB- 7/31/2008 Perpetual 9/12/2008 2/22/2013 DRE
DTK Dtsche Bnk Cap Trst 3 7.60% Aa3e 2/12/2008 A 8/01/2008 Perpetual 8/15/2008 2/20/2018 DB
LEH'J Lehman Brothers 7.95% Baa1 7/17/2008 BBB+ 6/02/2008 Perpetual 7/30/2008 2/15/2013 LEH
MTB'A M&T Cap'l Trust IV 8.50% A3 1/24/2008 N/A N/A 1/31/2068 9/10/2008 1/31/2013 MTB
C'P Citigroup, Inc. 8.125% A2 1/18/2008 A 6/03/2008 Perpetual 8/01/2008 2/15/2018 C
The symbol appearing to the far left can be brought up on Yahoo Finance, for example. Some quote engines will not recognize all of those symbols, but they are all recognized by at least a few. Bloomberg's website for instance, does not recognize the Deutsche Bank 8% symbol
DKT but the
Marketwatch website does. Note the Marketwatch quote shows the dividend as $0.50. That is the
quarterly dividend. The share pays $2.00 per year. The Yahoo Finance quote page does not give the dividend on that security. The point here is check several sources.
The "coupon" is based on the $25.00 par I mentioned above, so the Wells Fargo Cap XII 7.875% (symbol BWF) pays a dividend of $1.97 per year (25 X .07875). BWF closed Friday at $22.35 so the yield is currently 8.81%.
Financials are not the only sector to offer these types of issues. Many other types of firms have issued them from Utilities to Industrials and so on.
The other sleeve you might look into is the Master Limited Partnership. As indicated in the definition I linked above, they primarily deal in Oil & Gas, Real Estate and other commodities. You can find information about a few of the available MLP's
here. MLP's do not issue a 1099 form, rather a K1 form and one drawback is that they tend to issue them later than most firms issue 1099's.
The website
quantumonline has lots of information on income producing securities. They require you to sign up but there is no fee.
I hope that helps a little.