Open Forum

Some operations - third party or otherwise - are more supportive of an organization's mission than others.  I recommend that you evaluate this proposal strategically based on its ability to advance your organization's mission.  

For example, one might reasonably assume that your own museum's gift shop offers for sale items that are closely related to your museum and its mission (e.g. exhibition catalogs, post cards depicting historical images from your collection, other collection-inspired gift items, etc.).  In addition, its sale proceeds may support other more direct mission-oriented activities.  These benefits - in addition to your institution's need for a front desk to greet and orient visitors, answer questions, etc. - has already warranted your Museum's decision to allocate space and personnel resources to its operation.  

In contrast, the local book store's sales stock is almost certainly much broader, with only a small portion, if any, related to your institution and its mission.  Consequently, its primary and possibly only value in advancing your mission is likely to be limited to the financial support it provides your museum (through both rent and potential reduction of your personnel costs in manning the gift shop and front desk) as well as any incidental increase in visitors caused by this ancillary operation.  You need to ask whether the "cost" of turning over a portion of your first floor is worth this support.  The "cost" of this proposal to your museum might include the loss of the ability to use this space for other more mission-related activities and potential marketing confusion of the museum's identify with that of the book store.  When the book store is staffing your front desk and gift shop are they answering questions about your museum and its activities or are they promoting the latest best-seller?  What do they do when one activity takes time away from the other?  Will they be responsible for giving knowledgeable and mission appropriate information in response to visitor inquiries?  How do you ensure that?  If a customer is dissatisfied with their experience in the book store, does that have the potential for spilling over to negatively impact their feelings about the Museum?  

This proposal could be a wonderful synergistic partnership or a potential disaster - the yardstick you need to evaluate it is the degree to which it will advance, or impede, fulfillment of your mission.  Only your institution can make this determination for your specific situation; you should proceed meticulously assessing all the related pros and cons.  

Best wishes!