Buyer Keywords In The Accounting/CPA Niche?

So, I have a lead that is in this niche who asked me to do an in depth proposal. He works with high end clients right now, but in a way that he doesn't like as he's tied to a company that's not his, and a bunch of contractual BS.

He's going out on his own, and wants to have his own base of services before trying to woo some of the higher end clients away from the firm he's currently at...

I'm not bad at local offline keyword research, but I don't know that much about the way accountants operate beyond tax prep, Quicken audits, certain types of deductions, and tax shelters for the wealthy and/or expats.

Any ideas? I mean... I know the hot button issues in the roofing industry, in auto care or in the medical industry for the most part... but financial has never been my thing.

I know I can help him, but when I ask him "what are the top things you help people with, and what are your most profitable services" he just states general things that are not really buyer oriented... or maybe I just don't know how to spin them in that context yet.

ETA: I am not doing indepth keyword research for his proposal... he doesn't care, we spoke on the phone today and he is happy with the basic plan I laid out... he is just visual and wants to be sure he's understanding where his $$ is going. I just want to know these things for my own sake.