I'm not expert enough to advise you, but I suggest you look into whether you're likely to use the kit lens u/w in the long term.
I have a D80 that came with an 18-135 kit lens. It worked fine for a walkaround lens for the first year or so I had the camera.
I was gifted the Ikelite housing and the port for the 18-135. I found out on the first trip (as the websites had warned me) that the 18-135 was not a great lens u/w.
So I made some changes to my lens inventory (including selling the 18-135), and now don't need the port that fit the 18-135. Since it doesn't fit a wide range of lenses, I haven't found a buyer for it.
I tell you all this (not only as a
shameless plug to sell my port), but mostly because I encourage you to think through your short- and medium-term lens plans before you buy ports.
Especially if funds are tight, I don't want you to buy a port that you end up not using once you change/expand lenses. If you have the time, do the research to figure out if you're going to use your kit lens u/w enough (others on this very forum can probably help advise about that) to justify buying the port for it. If not, make sure the port that fits your kit lens will also fit a wide-enough range of other lenses that it won't be useless if you replace the kit lens.
Best of luck. You're going to love shooting u/w with an SLR.
FWIW, I ended up with:
Nikkor 105 macro and flat port 5505.46
Tokina 10-17 fisheye w/a and modular dome port 5510.45/5510.11
Nikkor 18-200 that never goes underwater, but is on the camera the rest of the time and I love it.