Thinking about buying a kayak. My price range is between 100-650...Idk if thts big enough. I have no clue what Im looking for even though Ive fished in plenty of them....

That's a good price range for quality used ones.  A lot of folks buy kayaks and realize it's not what they thought it would be.  The two main questions are do you want to be able to stand up in it and how are you going to transport it.  In general, shorter kayaks are better when fishing, longer kayaks are better for paddling.

 

Just as an example:  You can get a barely used Tarpon 120 in that price range;  you can't stand up in a T120, the weight isn't too bad (for transport), it is a perfect length for fishing and paddling and it's design and layout became the standard for fishing kayaks.  I haven't met a T120 owner that was unhappy, most folks upgrade to a kayak that allows for standing.

 

Hope this helps and good luck!