Quest Electronics offers an affordable new unit for about 10k...nice
image resolution, too!
www.questelectronics.com
FF, from what I've read, the price a "homebuilt" is based on the
scrounging capabilities of the builder. I lurk around old boat shops
here by the Bay and fish-finders are "dime-a-dozen". Gathering
the compatible bits in $$..depends, like anything else on how much
of a "hurry" you are in. Find a mad divorcee and the price gets cheap.
Here is a very informative website of a fella that has built quite a few.
Dans Homegrown Side-scan page
www.portup.com/~dfount/sidescan.htm
At the botom of his page is a link to an "active and current" side-scan
forum..I'm sure these guys can answer any of your questions.
Happy Hunting!!