In all, it is going to depend on where you are located. In Central Texas, the water is VERY hard but I chose to not soften my whole water system, just for the espresso machine. If you are not familiar with hard water, this is what causes lime build-up. It's a white, crusty looking build up that will kill your $8000 espresso machine and other equipment. It clogs up the piping that in time, builds up to the point of the water not being able to get through. Then your machine needs to be completely taken apart and de-limed (aka de-scaled). Not pretty and not cheap!
I had my one group de-limed for about $900 in the beginning. The 2 group needed to be done but I actually tackled that one myself. What an experience! Avoid lime scale build-up by getting a water softener.
Before you open a coffee shop, in my experience regardless of where you are you should get a water softener of some sort. Aqua Pure (formerly Cuno) makes an in-line water softener filter that will last for about 30-90 days based on your volume. The replacement filters are about $40, and can be bought by the case. This is not recommended for large volume stores as it can get costly. There are a variety of water softeners you can get, do some checking around.
I have clients using a softener called INOXDEP. It is a small, cylindrical shaped container that you add salted water (i.e. salt pellets) to every month or so. It's kind of a small, manual version of a large, whole house-type water softener. I have this same softener and I love it; it works great. If you are to have a lot of kitchen equipment like an ice maker, dishwasher, etc you may want to consider getting a large water softener for the entire water supply. Or at least the cold water supply.
I have another client that has only his hot water softened as he has a restaurant and he wanted to protect his dishwasher. The ice maker is on its own filter system and so is the espresso machine and coffee maker. So there are numerous ways you can go. Hard, bad, unfiltered water will not only kill the taste of your coffee but will kill your espresso machine and other expensive equipment. Do not overlook this! Ask me how I know!
Whole system softeners cost about $2000-4000 and may be overkill for some, but worth it for you so you do not have to change out a filter monthly. Just replace the salt. You may want to talk to your city water department about the hardness and overall water quality so you can plan accordingly.
If you are going to open a coffee shop, some industry gurus will tell you to go to a water softener specialist or get reverse osmosis but in my opinion, that is overkill. Just take care of the water for your espresso and coffee (and other important equipment if applicable) and do not worry much about the faucets. In reality, a whole house-type water softener from Home Depot will work just fine if that is the way you want to go.
On a side note, be sure to test your water at least weekly to be sure it is in the soft zone. A company called Hach makes test strips under the 'Softech' brand that will do the test job for you. You can get them online.
So when opening a coffee shop, just like where to buy coffee beans that are fresh a water softener can make you or break you because it can make your equipment work more efficiently and extend the age of it all. Hopefully these tips will give you some insight as to what to look for.