What's the competition like in that subdivision or area? If it's too heavily farmed already, you might be wasting your efforts and money.
Is the area large enough, or are you farming multiple areas? You can't expect to generate large amounts of business from an area unless the base is large.
Are the homes or properties in the area of the type, size and price range that you would like to work and can make a living at?
Many sales professionals have successfully used the funnel approach for sales projections. However you do it, try to come to a realistic estimate of return for time and money invested.
The consideration however is one of your time and how it might be better spent than designing, printing, consolidating and mailing postcards to the USPS specifications to get a discounted postage rate. If you already have office staff, this might be feasible. If not, how might you be better spending your time in generating business?
Try to find a service that doesn't require a long or minimum contract. Also, it is probably better if they provide an online method for you to maintain the list on their servers. You can still keep a copy of the list for other purposes, but it's like a backup and efficient for it to be kept by the provider of the service also.
If you use a tax base, it could be out of date, but at least it is usually free and you can use it over and over without further payment. Just clean it up as quickly as possible. You do this by using some form of postage that will get bad address cards returned to you so that you can remove those addresses.
Budget for the long haul and don't falter. Once you've chosen this marketing method, stick to it and you should see results that will grow over time.

