Depends on when this occurred. If it was donations given to him during his run for President -- extra funds are his to do with as he wants -- this applies to all campaign contributions to any running politician. If the funds are for his run for the 2020 election, then no, it is not legal.

Robbing the US Treasury, freedom from being prosecuted, nepotism and the power to legally lower his taxes are all the reasons he wanted to be president to start with.

Criminal profiting from his occupation of OUR White House!!

Didn't used to be. Who knows now a day. Back in the 90's they stopped that - made it illegal. Used to be a retirement fund for some Congressmen, as at retirement all that money became theirs. That was especially profitable for Congressmen in very safe districts.