Could the president shoot someone on Fifth Avenue and not be prosecuted?Yes because otherwise he wouldn't be able to do his job. How could the President run the country if he is tied up in court?
That is why the founders set up impeachment.
Could the president use his personal properties as federal grounds for profit?
Could the president use the powers of his office for personal financial gain?
What laws, in your mind, do not apply to a president? Murder? Theft? Extortion? Bribery?
The answer to all of that is... yes. Now, once the President leaves office he becomes a private citizen and subject to all of that. So if the statute of limitations hasn't run, then he can be prosecuted. Until then, the only thing that can impact him is impeachment and conviction in the Senate.