I think you might be wasting your money.
Where I live, the local Home Energy Advisory Team (part of the local government) did a check (not the full thing), and gave advice. It cost money, but if you did any of the top 10 things they advised you to do, you got a full refund and a rebate of up to $1000. They have since stopped the whole thing. The things to do ranged from putting bubble wrap in the skylights (virtually free, and one way of insulating a skylight), to installing double glazed windows, but most of the things they advised were really cheap to do, and when I did them, the outcome was excellent.
Later, they had a home energy kit available in the library, where you do it yourself with the supplied compass, kill-a-watt (a meter that you plug your appliances into and then plug them into the wall to see how much each appliance consumes), infrared detector (you move this across the ceiling, walls etc. on a very hot, or a very cold day, to see where you have different temperatures = bad insulation or any air leaks)... and a book that you fill out that has advice on what to do about what you find out.
Through discussion on this site, I have found that most libraries (here in Australia, in the US and in Canada) have some of the gadgets in the home energy kit available to anyone.
I suspect that you will get as much out of getting the gadgets that are available in your library as you will from your audit. Not only that, but you can borrow the gadgets multiple times, to check for problems and to check that they are fixed.
The infrared detector is a fantastic toy, and I know people who have really had a lot of fun waving it around inside their house. I might even go as far as to say that it has been difficult to pry it out of male hands to return to the library! And it is very informative.
Once you have used these things, and altered your house to address your findings (added insulation where it is needed, caulked, added pelmets...) it might be worth getting a professional to come and find the difficult things. Otherwise, they will only find the types of things you will find with the infrared detector, and you will have wasted your money.