Instant messaging (IM) is chat with one other person. using an IM tool like AOL Instant Messenger, Microsoft Live Messenger or Yahoo Messenger.
The tools allow you to indicate whether or not you are available for a chat, and if so can be a good alternative to emails for a rapid exchange.
Problem arise when people in a group are using different IM tools that don't connect. One way around this is to use a common Voice over IP tool like Skype that also provides IM.
The most familiar instant messaging today is computer-to-computer instant text messaging, but IM also can work with mobile devices, such as digital cellular phones, and can incorporate voice or video. If fact, you can't go anywhere without seeing some text messaging.
Although there are a number of free Internet-based messaging services, IM is a feature that carriers can offer to increase customer loyalty and add value to their service offerings.
In order to set up an instant message, you have to add the usernames of the people you want to message with to your "buddy list" (friend list, contact list). When they log in to the Internet with their IM software, and provided they have not configured themselves as "invisible," you are instantly alerted. When they log out, you are also notified. Each system has its own method for blocking incoming and outgoing messages.
IM marketing is not easy since you must be connected, a buddy with the person you are IMing. Since it's not wise to use IM to send marketing messages to your friends, family and collegues, you might be able to ask them to spread the word with a tweet, posting on Facebook or LinkedIn or other social media network.
I wouldn't budget much for IMing: $25 - $50 a week