The two certification programs that address blower door and duct leakage testing are:
You'll need to take all the required coursework and pass a field exam for each. The BPI IDL program is a shorter hurdle for an HVAC tech looking to add blower door or duct leakage testing services, while the RESNET HERS Rater is a more intensive program. It covers the science behind the blower door and duct leakage testing, but the also the rest of the "home as a system" as well. (eg. insulation, etc)
At a minimum, you will need:
Although there have been a few new entries vying for market attention, there are two manufactures of these products that dominate the market for blower doors and duct leakage testing equipment. Their prices vary little more than their abilities. Both typically include their gauges and their prices are below.
The Energy Conservatory
NOTE: These prices typically do not include shipping fees however Vent Cap Systems always sells them with free shipping and typically with some additional incentive.
At the end of the day, you'll spend between $5,000 and $6,000 on new blower door and duct testing equipment.