Looks like you're looking for credits.
Anyone who's offering a Cobra is probably not the style of explorer you're looking for. Whenever I hear anyone offer a Cobra as an explorer vessel, my usual response is to twitch violently. There are two types of explorers: the straight-line explorer, who's willing to fly anywhere, get the discoveries they want, and go home, and the meandering explorer, who, well... meanders around, scanning whatever they run into. If you're wanting credits, you're almost certainly intending to act as a straight-line explorer. A Cobra is decent for a meandering explorer, but is not a good choice for a straight-line explorer because of the short jump range. If you're looking for a target number of credits, you're going to want an explorer with decent jump range - which means a Diamondback Explorer, an Asp Explorer, or an Anaconda.
If you want armament, I would recommend leaving the weaponry at home for exploration, then remounting them when running missions in inhabited areas.
Not sure how much you have in the way of credits, but I'm guessing you could probably afford this ship, a Diamondback Explorer with top-of-the-line FSD, fuel scoop, and DSS and ADS. Didn't put a landing package in, because at this point you're looking for credits.
http://coriolis.io/outfit/diamondba...1D3D4C-------320o432i2f.AwRj4lS6SA==.Aw1-kA==
You then take this ship out to the neutron star fields about 14000-15000 light-years from Sol, and scan neutron stars and black holes until you reach your target credit amount. And yes, you can earn exploration credits VERY quickly in the neutron star fields.
Observe that a slightly-smaller fuel tank is installed in this build; the DBX's fuel tank is oversized for its FSD anyway. By switching to a 16T fuel tank, we increase the jump range to 35ly, while still keeping a 3-jump-and-safety build.
If you can afford a slightly-better explorer and want something with an SRV, you go with the Asp Explorer, here:
http://coriolis.io/outfit/asp/02A4D5A4D1D5D4C----------3c0t0i-v62i2f.AwRj4jRZYo==.Aw18WQ==
Again, we've gone with the smaller fuel tank, to increase the jump range. Again, take this ship out to the neutron star fields about 14000-15000 ly from Sol, and have fun.
I'm guessing, if you're asking about credits, that you're not in the range for an Anaconda. If you are, then this build will work:
http://coriolis.io/outfit/anaconda/...-----3h1211----v4432i2f.AwRj4yVTjqxA.Aw18ZlA=
Anyway, main takeaway: If you're exploring with an eye for hunting for credits, that means getting to where the credits can quickly be gained - and that means using a ship with a good jump range.