I can't think of many 707 jobs out there. Off the top of my head, John Travolta has a 707, i'm sure he needs a second pilot and an engineer, there is Omega Refueling
Omega Air Refueling , but they are looking for people with 1500 TT, 500 on type (looking for ex 717/KC135 guys really). Then there's the USAF, if you're a US Citizen and under 29 with a bachelor's degree, you could check out the various ANG units that fly the KC-135 (although technically not a 707, the FAA will give you a 707 type rating on your cert). Active duty USAF, you have the opportunity to fly one of many C-135 airframes, or one of the few C-137s, E-8 (JSTARS), E-3 (AWACS), or in the Navy E-3 Mercury (TACAMO).
Here's a list of 707 operators:
List of Boeing 707 operators - Wikipedia, the free encyclopedia
And from the FAA:
N-Number Results