How much to build a dock?

I'm looking at buying a home on the water, and I have the option of rolling the cost of the dock and lift into the loan (having the builder construct it), or telling him to not do it, and then hiring an outside person to build it.

Either way, I'm just asking, what is the typical expense of a dock with a lift? I'm not talking anything too fancy, maybe 15-20 feet wide at the widest, with a couple of walkways and a slot for the boat with a lift (and covered canopy or roof over the boat).

Estimate anyone?

thanks