Years ago in california I had similar with a mentaly challanged nephew. His dad died young and sister had 6 kids. For whatever unexplained reason 3 of the 6 had mental issues from brith. It struck them at pubity. I stepped in and took two of them on. With one I was his social security payee and handeled his affairs, paid the rent etc. He died on me in 2004 at about age 42.
From my experiances I urge you to keep accurate accounts of finances. Every once in awhile with no sechuel, the goverment will want to look at your bank statments if you are handeling it.
Good luck. I was raised in wisconsin too.