First of all an energy audit and an RESNET energy rating/analysis are different entities. An audit can done by by almost anyone. It may not require any equipment. Many local utility companies will do one for no charge. It is basically a visual inspection and when done under Home Energy Pro requires some building measurements. I do not know of anyone that is doing audits except maybe window salesmen and HVAC salesmen. The HERS Energy Rater goes through more training and certification. You can go to RESNET: Residential Energy Services Network | Setting the Standard for Quality for all the info on how to become a rater.

Costs - training about $1500 - travel/hotel at training - $700

Equipment - 2 companies - energy conservatory | home and Retrotec Energy Innovations Ltd. : Home. I went with Retrotec for about $4300. I already have enough customers - one builder with 5 houses and another with 6 that are going to use me. A HERS Rating Index/Energy Star analysis (includes paper work - house diagram and Remrate computer report, 2 visits, and blower door and duct blaster tests. I charge $.20 a sq ft of living space. This is slightly below the going rate. My 11 houses average 4000 sq ft so I'll make about $8800 which will more than pay for my investment. Every Energy Star built requires the analysis of a RESNET certified energy rater.

I thought a long time before attending training and even longer before buying the equipment but it appears that it is going to be a worthwhile investment.