Imagery can be acquired through aerial methods (aircraft with a digital camera or other types of sensors) or satellite based methods. Satellite imagery can be coarse (30m or 10m resolution) for large areas, which is good for landscape applications but often lacks the detail required for local governments. Finer resolution satellite imagery (0.6m - 2.0m) can provide excellent detail and is repeatable (images are available for each pass of the satellite, though clouds can pose problems). However, as a general rule, the higher the spatial resolution, the more expensive the imagery, which can pose problems if you need coverage over a large area. Check to see how much coverage you need and at what resolution. Over larger areas obtaining aerial plane based imagery is probably going to be the most cost effective. You will want to determine how you will want to use the imagery, and what resolution meets those needs. You can also decide between color, color infra-red, and black and white. Compare the per foot (or per unit) cost of imagery between like satellite and aerial imagery products.

One of the best things to do when you begin planning for image acquisition is to find out if your state has acceptable imagery you can use. To determine the status of state-conducted imagery programs, contact your state GIS coordinator
National States Geographic Information Council (NSGIC). If the right data do not exist, you should try to see if other local or regional entities want to share in the purchase. The highest cost is going to be putting the plane up. It's more cost effective to do multiple locations then a a single municipality or county.

You should also look closely at other contracts and deliverables from local governments around you. Your state agencies may be able to give you advice on contracts and deliverables. You will want to make sure the end product you receive has an accuracy assessment and good quality control. Seek multiple bids from reputable companies to compare different end products and deliverables.