Reddit reviews Power Man & Iron Fist Epic Collection: Heroes for Hire (Epic Collection: Power Man & Iron Fist)

For Daredevil: The Bullseye/Elektra Saga, which is rumored to be what DDs2 is based on, at least partially. It is collected over three trades, OR you could get this brand new reprinting of the omnibus here: http://www.amazon.com/gp/product/078519536X?psc=1&redirect=true&ref_=ox_sc_act_title_1&smid=ATVPDKIKX0DER

For Jessica Jones, I'd say try Alias, that is what JJs1 is based on (again partially). You can get the first volume here: http://www.amazon.com/Jessica-Jones-Alias-Vol-AKA/dp/0785198555/ref=sr_1_1?s=books&ie=UTF8&qid=1452066126&sr=1-1&keywords=alias

Now for Luke Cage and Iron Fist, I'm not sure what the series are going to be based on and I don't really read their individual titles, but Marvel recently released an Epic Collection of their early adventures together as the Heroes For Hire, so I would start with that, which can be found here: http://www.amazon.com/Power-Iron-Fist-Epic-Collection/dp/0785192964/ref=sr_1_1?s=books&ie=UTF8&qid=1452066331&sr=1-1&keywords=power+man+and+iron+fist

The Defenders are actually very, very different in the comics, Jessica Jones isn't even a member of the team. Although all of the characters are very close friends in the comics and appear in each others series fairly often (when Jessica, Luke, and Danny have their own series that is). I know that Luke Cage, Jessica Jones, and Daredevil are members of the Mighty Avengers, but have no idea if Iron Fist is also a member (the Avengers history and line-up isn't really my area of expertise). When it gets closer to the release of The Defenders on Netflix, however, I'd almost put money on Marvel restarting the Defenders with the line-up of the series, so look out for that.
Hope that helps!

http://www.amazon.com/gp/aw/d/078519164X/ref=mp_s_a_1_7?qid=1453605276&sr=8-7&pi=AC_SX118_SY170_QL70&keywords=iron+fist&dpPl=1&dpID=61bau-bXUSL&ref=plSrch

http://www.amazon.com/gp/aw/d/0785192964/ref=pd_aw_sim_14_1?ie=UTF8&dpID=618-A7YPKwL&dpSrc=sims&preST=_AC_UL100_SR100%2C100_&refRID=0MA0CAGCZ1QHQNDGQ82E

http://www.amazon.com/gp/aw/d/0785185429/ref=mp_s_a_1_2?qid=1453605276&sr=8-2&pi=SY200_QL40&keywords=iron+fist&dpPl=1&dpID=51vwq4AXhJL&ref=plSrch

There you go, sport.