I worked for a gentleman who had a lady that worked as caregiver (mostly covering for girls or if one quit, she'd either cover those shifts or delegate it to whomever) but she ALSO controlled his finances AND also does all his taxes. And, I have also WITNESSED on three separate occasions, where he has told her she could "go ahead and write herself out a check" and each time it was over $500 (this was separate to the 'paycheck') she received also. She also once told us we all had to go in to work to help him move into his new apartment BUT that we were not to be paid for it, and were required to do so out of the kindness of our hearts... that was also the first time I watched him have her write herself a check for $500 for doing the same/less work than ALL the rest of us girls (about 4 of us) for a shift we were all told we had to do pro bono.
As an employer, I would never "tell" my people they had to do something "pro bono". That's why it's important to know who you are actually working for -- this way you know what labor laws protect you (or not if you are getting paid in cash).
You could report the situation to APS but if he's competent, and you don't have any other evidence other than she wrote "a" check for $500 once - then I don't think that will be investigated.
Also, is he signing the checks or is she? Who is your actual employer? Him or her?
Seems inappropriate that she is controlling his finances - but I'm not 100% sure what you mean by that. Is she not allowing him access to his money? Is she just paying his bills for him with his money because he can't do it? She may be doing it right and out of the goodness of her heart. Or not.
Taxes - does she know what she's doing? Maybe yes, maybe no.
How did this woman make you and the others move him for free?? She couldn't literally physically make anyone do anything. Did she threaten you with bodily harm? Or that you would not get anymore work from her? Do you actually work for HER or for the man?
Looks like time to look for a new job and stay away from her.