Mike, you’re a licensed contractor, right? Don’t buy Water Heaters at Home Improvement Stores I always bought stuff like that from trade supply houses. Takagi’s aren’t too bad, just make sure you understand Pros and Cons of both set ups. Try getting a trickle of hot water from a tankless… try it.
Seriously though, If you are a lic/regst’d contractor, a plumbing supply house may offer you a better product for less money.
The plumbers I know would shoot me if I bought the brands at HI stores, they have problems (you can look at the brands next time you’re there). I’ve had a couple of plumbers tell me that I should look pretty hard whenever I see one of those tanks installed, as some Homeowner went and bought one and “hooked it up”… Don’t prove 'em right Mike!
As far as not knowing how to sweat, you may be better off dealing with compression fittings/couplings if you’re not familiar with sweating copper. You wouldn’t be saving money by buying a decent torch and other tools. http://www.doityourself.com/stry/cutjoincopperpipe