As per the NY Times today:
The warrant that authorized the FBI to search Pres. Trump's Florida home, which was unsealed this evening, listed 3 criminal laws as the basis of its investigation:
1) Section 793 of Title 18 of the US Code better known as the Espionage Act - which criminalizes unauthorized retention or disclosure of information related to national defense that could be used to harm the US or aid a foreign adversary.
2) Section 1519 which "sets penalties for the act of destroying or concealing documents or records "with the intent to impede, obstruct or influence the investigation or proper administration of any matter"
3) Section 2071 which "criminalizes the theft or destruction of government documents."
The magistrate judge who issued it found that there was probable cause to believe the FBI would uncover evidence of all 3 crimes.
In response, Trump said all files seized from his home had been declassified (something he would have done himself before the end of his presidency) but none of the crimes depend on whether the documents are classified.
The warrant cited obstruction of justice as one of the potential crimes justifying the search, and the possible mishandling of government records as listed as the second potential charge.
NY State has already investigated Trump in the case of Trump University and the Trump Foundation. I doubt the NYAG would bring the case to this stage if there wasn't any evidence leading to an indictment. That said, I'd doubt Trump would face any prison time or serious charges resulting in prison time but from what we know so far, the likelihood of indictments is not small.