You will need at least one, and possibly more, telephone lines, depending on the scale of your proposed business.
You will need to be able to receive customer queries and bookings by telephone and fax, and you may find it useful to have an email address. A website can be a good way to promote your business.
The telephone company will bill you every month or quarter for the calls you have made, often plus an amount for the line rental for the next quarter.
Many different internet service providers (ISPs) offer internet connections and email accounts. Shop around to find the best deal for the package of services your business needs.
You may decide that your business will benefit from having mobile phones as well as, or instead of, land lines.
Various packages and discount structures are available to business users which can help to reduce telecommunications costs. Contact your telephone company's customer services department for details.