We're just getting into pond building ourselves, have one under our belt.
I'll try to answer your questions for you...
If you listen to Greg Wittstock of Aquascapes, an 11x16 pond installed is about $3500.
You'll have to check your local area to see what material costs are. You can buy the kit from Aquascapes, it has all the liner, underlayment, plumbing, etc. Get the bulk mat'ls locally.
In fact, you'll be best off ordering a video from them or their major competitor, Pond Supplies of America, led by Greg Wittsock's dad (no kidding).
Do you have to check city ordinances - only your local municipalities can tell you that. Where I live, the pond can't be more than 2' deep without having a fence around it.
In WI, no license required. I think this field may bo too new to require licenses anywhere, but you should check to be sure.
I'm not aware of any additional lines of ins coverage required for this.
Tools to do the job? Depends on the pond. You'll need a small toolbox worth of stuff to do the plumbing, the rest can either be done with shovels and rakes, or excavators and skid loaders. The one we did was about 30'x20' and we excavated with a skidloader.
One thing to NOT do: I've been to seminars (whose sponsors will remain nameless) who recommend running extension cords under mulch to wire up the pump for the pond. DO NOT do this. Hire an electrician, or have the customer hire an electrician, or let the homeowner do it themselves. If you try to wire up a GFCI outlet as a non-electrician, you open yourself up to all kinds of liability. And extension cords under mulch, well, that's just not smart. One homeowner sticking a spade through a cord connected to a non-gfci outlet and you likely bought yourslef one french-fried customer and a one-way ticket to the poor farm.