The easiest answer would be to expose your BC API for Customers/Vendors.
Create a simple Excel sheet with the names of your potential clients, create a Flow which will connect the online website API, using the client name and if confirmed use the flow to Insert the Client details into BC Customer or Vendor.
Or you can take a look at the Marketing Module which will have you create Leads and convert them to Accounts. Here you will be able to track your email/phone conversations with them.
I hope this helps!
