So, I've always fished from the bank for the most part, and even when I would go w/friends on a boat, I never really paid a whole lot of attention to the electronics... I now see I probably should've paid more attention, as I am now in the market for either a kayak, or used boat if I can find one that is affordable. So what do I need to know about electronics? Do I need them? What should I look at for an affordable unit? What are some other tips you can give to someone w/no experience?

A basic unit (2D sonar) will show depth and the shape of the bottomn plus stuff suspended in the water column. At a minumum you would have a grey scale display and as you add features, the cost increases.

 

This is how a color display would show the bottom when you cross over a creek channel:

 

 

Properly adjusted, it will show stuff in the water column like fish:

 

Here is an article you might find helpful.

http://www.bassresource.com/fishing/depthfinder_fishfinder.html