He would be subject to nightly excoriation from all sides.
The folks who voted him in would be devastated by most of his policies. Fox News will tell them to revolt.
He would be in immediate danger of being impeached.
He would be completely unable to move congress or the courts, because they will all hate him.
His real estate ventures would certainly take a hit, and he likely wouldn't be able to do much about it.

Running for president is fun, and for Donald, cheap fun. It'll pay off in his private efforts.

Actually BEING president means there are about a million ways to fuck yourself and the country up every day. Accidentally leak the wrong information? Accidentally intimidate a judge? Accidentally forget to disclose some income? We can be talking censure and/or impeachment. I think Donald knows all this. He's not built for 3am in the situation room 3 nights a week. Dude needs his beauty sleep.