I have a float tube, pontoon, "Watermaster", and a Kayak. They each have their good points.
Just my opinion, but if you're fishing primarily freshwater you're probably better off with a float tube (I believe it's a little more versatile and a little more convienent to travel with). One of the advantages is that you can keep an eye on your rod while "trolling". Also the cost of "customizing your tube with (PVC) rod holders etc. is rather inexpensive and there are a number of threads on how to build your own here or get some ideas.
As for the rest of the costs, as with anything it will depend on your budget (which I understand is=to "Student broke").
Depending on what kind of waders you want to purchase this could be the second most expensive purchse after the Tube but a number of members here have found some good prices and sales on these. Suggestion is to keep an eye out on the threads for some help. My suggestion is to check
www.SierraTradingPost.com you might find anything from waders to swim fins {I found my Patagonia Watermaster Light waders (normaly $289ea)for $99} and I bought 2.
Great warm weather waders. As for fins any cheap swim fins will work in a pinch until you get more $ to upgrade. As for maintenance there basicly is none (except cleaning/rinsing/drying after each outing to prevent mold and possible transporting of any invasive species).
For all around versatility I do "Love" my Watermaster, because it packs away into it's own backpack complete with oars pump and any accessories I care to bring along and I can Kick or paddle and cover alot of water because of the oars. On top of everything else I feel completely comfortable fishing inshore harbors. However the cost of one of these is prohibitive so I need not expound on this further.
Although I love my Kayak, the one drawback is it's weight and portability. There is an unexpected cost to owning a kayak that is not discussed very often...accessories. If you don't get a seat you like or if the yak comes with one that's not by choice, you can end up spending another $150+ for a "good" quality seat [like the Seairsport Pacific Angler I just bought with a group order for $125+tx (normally $179+tx). Then there are paddles. I have a Bending Branches Glide Paddle which retails for $125+ and I'm trying to save for a Werner Kaliste or AT Fishstick Paddle either of which cost over $350, and you'll find a good set of ergonomic oars like those are very expensive (even more than a used Kayak) and you will very rarely find these on CL or Ebay. On some of the Kayak forums I've participated on the overall consensus is that once people buy one of these, unless they are getting out of kayaking altogether they would never part with them. So you see even a Kayak will have extra costs that you may not nave planned on after the initial purchase.
I hope this is some help to you,
remember this is just my opinion/
LW