JDP~ I understand the poor college thing. I ate ramen noodles and potatoes for about 2 years. It sucked. The thing with freediving/spearfishing, usually once you have the gear it will last you 5 years+. No expense in filling air tanks or other extra costs that come while Scuba. Here are
MY recommendations:
Fins: Cressi Pro Star full foot fins: $49.99 (Basic Freediving fin that will last)
Wetsuit: You want a
2 pc, 5mil, open cell interior. (This should be LAW for Freediving in Wisconsin) I would think the cheapest you could go on this is around $200. This is a great suit for the price:
MAKO (Yamamoto) 2 piece green camo wetsuits in 3mm, 5mm and 7mm
Snorkel: Go with a simple "J-Snorkel" I believe you can get them as cheap as $9.
Gloves and booties:
HammerHead Spearguns The best Gloves and booties. They are open cell - get 5mm. And if you think you wear a Large Glove- go with XL - they run small. Gloves: $36, Boots: $20= $57-ish.
Float & line: You could make your own, if you do some thread searching you can find ones that people made themselves. Otherwise $30 could get you a float and go to a boat supply place and just get their Floating line. you should only need about 30 feet. Its cheaper than actually buying a "Float Line".
Gun: You want a gun about 75cm - 90cm. 75cm is about the ideal length for Wisconsin Waters - maybe a little longer for Lake Michigan. I still kill lots of fish in Lake Michigan with my 75cm. I use a Hammerhead and they have a new one out that runs $150.
Mask: go with a Low Volume if you can. If you can find it: AquaSphere mask is the best one I have found. They run about $40.
As far as you only being able to dive to 18' with pain. Stop doing that! lol. You're doing something wrong and you don't want to do something that is going to cause permanent damage. I HIGHLY recommend taking a freediving class. We are offering one July 27-29 at our FREEDIVING PALOOZA - it's put on by the best instructors in the world. They will teach you the techniques to get you diving to 66ft+ and have a breath hold of 3mins. This is a 2 day class that cost under $300!!!! This is an unbelievable deal. Will take your spearfishing to another level and could save your life. I will edit this, as I get more info for you
You should be able to get this decent gear for a little over $500 + $300 for the class - this isn't bad to set you up for life. Remember, this is why they make Credit Cards.............. :-D