In addition to the comment above, you can also have the situation that your sales person is also a customer - what do you do then? this is why you need a bridge table.

Your entities in one table with an EntityID as a unique key

Your address table with an addressID as a unique key

The bridge which would look like (e.g.)

(possibly have a surrogate key such as EntityAddressID)

EntityID

AddressID

AddressTypeID

(I would also add EffectiveDate (i.e. you may enter future addresses but the sales person, customer has not 'moved in' yet), it also allows you to keep history; add Status (Active, Inactive); etc etc)

I hope this makes sense,

B