A complaint to APS can result in civil or criminal prosecution by the county/state. Consequently, the matter could spiral into something extremely bad, if APS were to believe that you are actually engaged in financial exploitation of your mother. On the other hand, if APS comes back with an "unfounded" conclusion, then that will be the end of the matter.
Hiring a lawyer is a costly exercise -- if you have absolutely nothing to hide. But, there is no way for me to evaluate whether or not your financial actions concerning your mother have inadvertantly crossed a line into unlawful conduct. Unfortunately, given the complexity of financial issues, a local attorney would have similar difficulties, and the cost of a full audit of your financial dealings (involving a CPA and an attorney) would be horrendous. So, you need to consider whether or not you want to burn what I would estimate as being at least $7,500 in legal and accounting costs to prove to yourself that you have done nothing wrong -- vis-a-vis simply opening your books to APS and letting the cards fall as they may.
The point of having your own private audit, would be so that you could turn to APS and tell them to "stick it where the sun don't shine," when they start asking you questions. The result of which may be a petition by APS to establish a public guardian, so as to force you to disclose your records -- which you would know via the audit prove you've done nothing wrong.
BotXXXXX XXXXXne, unless you believe that you have done something really questionable -- e.g., bought yourself a car, a diamond tennis bracelet, taken a vacation to Cancun, etc., you probably have nothing to hide and no reason to either hire a lawyer or to withhold info to APS.
But, if you have don something untoward, then my suggestion is that you immediately stop answering questions to anyone, and if you are asked, your sole answer is: "I respectfully XXXXX XXXXX right to remain silent under the U.S. Constitution." And, then, you may want to hire a lawyer to protect your interests going forward.
Hope this helps.