If you do not already have two telephone lines in your home or office, your telephone service provider may have fees for setting up a new line, and/or monthly charges on that line.
The second line may be very basic, without long distance or advanced features such as Call Waiting or Caller-ID.
Otherwise, there are no separate costs associated with 2-line CapTel service. (CapTel users are responsible for any long distance charges they make.)