I fully agree with PhilC and Grant. This has a very bad smell to it.

As suggested by PhilC, I think the first course of action would be to have the treasurer ask the co-op's accountant for copies of the last five years of audited financial reports and annual budget projections. How the accountant reacts to the request will tell you a lot about how you proceed.

Another approach would be to contact the Real Estate Finance Bureau. They are a division of the NYS A/G's office. Either they can help you directly or point you in the right direction. If there is anything illegal going on with your building's finances, the A/G's office is who you want involved.

Your final recourse will be to have a group of shareholders hire a private attorney familiar with co-op and condo law. It won't be cheap, but ask the attorney if you can recover any expenses from the co-op and under what circumstances.

Have you considered putting up a slate of candidates to run for the board at the next election meeting? If it's not that far in the future, this might be the least painful way to gain control over your finances.

Best of luck to you.