We have completed a fair amount of tenant finish work for small spaces. The more cumbersome items to incorporate into those small spaces include the drinking fountain and the service or mop sink. The 2009 International Building Code (IBC) allows an exemption from the drinking fountain requirement if the space has 15 or fewer occupants. This was a nice upgrade from the 2006 IBC and can be easy to overlook.
There is a pleasant surprise in the 2012 IBC that should make landlord and tenant alike happy. If the space is a Business (B) or Mercantile (M) and the occupant load is 15 or fewer a service sink will no longer be required. The catch here also is that the code asks for one drinking fountain but accessibility guidelines almost always require two: the high and the low. These requirements could easily add thousands of dollars to a simple tenant improvement project which is a large unexpected burden on the business plan.
If you are looking for a place to put your small business I encourage you to look for two things: a space that already has an accessible restroom and location in a jurisdiction that has adopted the 2012 IBC. However, do keep in mind that many jurisdictions make amendments to the building code as part of their adoption so it always helps to hire a great architect who knows to check all the current rules.