If a survey is done, it would be at the request of your lender. Many lenders today are not requesting a survey as part of your financing - it saves you about $300-$350 in closing costs. But, it might be in your best interest to have one done regardless of whether or not it is required. The title company will order it and you pay for the survey at closing. Sometimes, you can obtain a survey from the previous owner and unless they did something to the exterior i.e. built a shed, put up a fence, etc. that survey may surfice for the purposes of showing you your lot boundaries.