so I actually was in your position a few years ago and actually got it done for Montana, and I will say it was a pain in the butt really.
Actually declaring residency is fairly easy, usually just a matter of getting a drivers license and either having a car registered or having a permenant address that you can prove you are getting mail sent to.
Thats the easy part, but my guess is your question has to do more with the WICHE program and its workings. Really the process is not hard as long as you can prove that you have been in the state for 12 continuous months. Thats where I had problems as I left often to go to school out of state. But if your applying next year and you are not currently in school it should not be a big deal. If you are in school and you didnt graduate from a Montana High school then you have a similar problem as me and well most likely will be screened out.
But barring that problem, in regards to your question the money questions are basic answers. iIf I remember the money questions are basic information questions, they may ask for tax returns but thats about it. Basically its more to prove how much money you have coming in and that your paying state taxes.
What sucks too is that they tell you that the WICHE thing is based on rank and priority blah blah... basically saying that even by getting verified there is no guarentee you will get money... so ya dont worry about the money questions just fill it out and send tax stuff if they ask for it... otherwise no worries....
Good luck... hopefully it will be easier for you then me... and hopefully it helps you out more then me. ha