Having all your people in one pile makes sense.
Having separate tables for Contacts, Clients, and Vendors makes sense.
An argument can be made for each approach.
Contacts might only have one email address and one phone number.
Clients might be an individual or a group of individuals with multiple contact methods and shipping addresses.
Vendors would likely have Purchase Orders associated that other people would not.
The people that did the Starter Solutions for some versions of Filemaker have a free open (complex) template called Starting Point.
These forums have no provision for Sticky ReadMe StartHere Posts, my list of Filemaker Links is here.
You could use an OnObjectModify script trigger on the radio button field to perform a check on the value in the field and if it is now "client", to enter the current timestamp into a timestamp field defined for that purpose.