Well, pertaining to starting your own CPA, these are the things I can think of off of the top of my head that would be required.
As far as the cost, I'm not exactly sure, but it wouldn't be cheap. If you are considering using DirectTrack, here is an excerpt from their FAQ page...
Each version of DirectTrack includes an initial licensing cost and a monthly hosting fee. The monthly fee covers product updates, support (levels depend on the version your business needs), and traffic levels.
You would have to request a quote to find out the exact pricing. Then you also need to have some reliable hosting for your actual CPA site (separate from the hosting DirectTrack provides).
If you are going to code your own affiliate tracking system, that would definitely make things cheaper, but depending on your programming experience it will take some time and might be better to hire someone to code one for you. This wouldn't be cheap.
But cost is only one thing. You would need to be experienced in the area of Affiliate Management and have support online at least 8-12 hours a day (the more the better). Affiliate support and tech support, that is. You would also need constant tech support for your CPA dedicated hosting server, unless you are going to do that yourself. When you are running a CPA and trying to compete with other CPA companies, I'm not sure if the standard dedicated hosting company's support would cut it. You might have to pay more for a really good hosting company and/or faster tech support. You might have to hire someone to help you with these things (or do them for you) unless you are forming a partnership with another person(s) and splitting the profits. Of course, all this hiring would cost money as well. You would need to review and approve new applications on the fly, constantly add new offers, see which are converting the best, etc. If you aren't good with web design you would need to hire someone to design your CPA site. IMO, it shouldn't be simple. It should contain the works (flash, CSS, etc.). A good search engine ranking would do you good too, but you wouldn't be able to use any BlackHat methods to acheive this, lol.
You would need to form at least an LLC, and depending on how fast you want that to get setup, it isn't cheap. Even if you don't pay for a faster setup it still costs a good bit. You will have to pay your Secretary of State $25/month (if in U.S.) and around $150-$160 to the Registered Agents of your LLC to keep everything updated and in "good standing" with the state, current and changing laws, etc. Last year my Registered Agent's fee was $150, and this year it was $160. I guess it depends on what state you live in or where you are.
Good site for launching an LLC:
Code:
http://www.legalzoom.com/
After purchasing everything you needed to purchase and getting things setup, you would need to have some extra money saved up (not pennies) to pay out to your first affiliates when your CPA is just starting out. That is, unless you want to insert a pay hold (at least at first), which wouldn't be wise because another thing with CPAs is competition. You would need to make your company stand out. You would need to be able to secure partnerships with some big companies that offer new, good converting offers often.
You would also have to keep up with your client's tax information and send out their tax returns every year. You could hire a CPA (not "cost per action", heh) to do this, but guess what? That would cost more money.
If you haven't noticed yet, a lot of time, dedication, money, and hard work would be required on a daily basis, especially at first but it wouldn't stop there.
I know there is a bunch of other things that I left out, but that is all I can think of for now. Everything I said is to the best of my knowledge, however if you have something to add or refine, feel free to reply.