Are you really asking us? (looks like your an agent and would likely know the answer to this?) Surveys are expensive, and not very necessary for most transactions. (unless the property is acreage, an unusual size/shape, and/or there could be possible encroachment issues). In Colorado we can order an ILC (improvement locator certificate), which is similar to a survey, but not as costly.
I'm not sure if they need to. I think that it is a good idea to just in case though. You will want to look into this more and see if there are reasons why you will need to have someone do this though. http://www.parkerscanlon.com.au/services.html
When buying a house it isn't the house you are buying -- it is the land it sits upon. So many transactions have problems with encroachments that no one knows because sales are made without survey required by mortgage companies. When I started 25 years ago, they were required and about 1 in 5 had issues that needed to be worked out before closing. Then mortgage surveys became acceptable--they were cheaper but didn't have the stakes in the ground or title safeguards. Most buyers here don't do it here in Kentucky either because they aren't required anymore. I buy investment property and we do a survey every time and buy title insurance. A regular-sized lot costs about $300-$400 for a professional survey. Is that too expensive to know what you own?