Good move. Make sure to specify the error margin (a building survey with an error margin of 0.5mm is three times the price of a rough survey with an error margin of 10mm) - ie tell them you want a cheaper rougher survey - make sure to specify the contours, and then ask for the resulting survey files in both Autocad and PDF format. You will be able to look at both and work on them for free so don't buy any fancy programmes.