Longcode is a method of communicating via mobile devices. Longcodes are the regular phone number format, and because civilians use these, if a carrier suspects that a longcode is being used to send "spam" / bulk advertise messages or receives a number of complaints, they may temporarily block the phone number. In the US, carriers have different processes in different states, so occasionally text messages may not get through to recipients using particular carriers in certain states. This is nothing that can be controlled on the sender's end but an issue with the carriers delivering the messages once they've received them. Longcode sending is at risk of carrier filtering or suspension for heavy traffic. Longcodes can send text messages up to 140 characters in length.
In a business setting, because of the restrictions and filtering policies of SMS messaging carriers, longcode is primarily used only for phone and fax messages, and to record for future reference and salespersons. Longcode SMS messages might be a once in a while occurrence, and will not be sent out en masse as it will cause your messages to be blocked by carriers and never reach their destinations.
No more than the usual fees associated with voice and fax messaging. We do have to charge small fees in order to pay for the services, but outside of those fees there is no additional cost associated with the channels, and in Fax, if a message isn't delivered you don't pay for it either.