Benedict has said he will devote his life to prayer. There is no playbook for the life of prayer for a retired pope, Hilgartner said. "Nothing beyond the normal routine or prayers for a religious or a priest."
He said that would include "prayer throughout the day and the liturgy of the hours, morning prayer, evening prayer, Mass every day."
Benedict is likely to keep a small staff at the house to tend to his needs. "He has some German sisters" -- nuns -- "who cared for him in his domestic needs at the Apostolic Palace and they're apparently moving with him to this monastery. So he'll provide for their spiritual needs, saying Mass every day," Hilgartner said.
There may be a stipend for the retired pope. Italian news outlets have reported retired clerics receive up to €2,500 a month. Hilgartner said Benedict won't need much money if any at all. The Vatican will take care of his lodging and his health care.
"He didn't have a pension because the presumption was he would be in office until he died," Hilgartner said. "His needs will be cared for. Because of the way he'll be living, those needs will be somewhat limited."
Back to the books
Benedict, a theologian by training, is likely to switch from universal pastor back to scholar.
"My sense is that he will lay low out of deference to the new pope, that he will stay out of the way and under the radar," Hilgartner said. He expects the pope to behave mostly like a retired scholar, doing lots of reading and maybe a little writing.
Benedict was rumored to be working on his fourth encyclical before he announced he would resign, Hilgartner said. Encyclicals are papal letters to the church, often on pressing matters that carry the weight of the office the pope with them.
"He had written the encyclical on hope, the encyclical on love, and another one on social justice and charity," Hilgartner said, adding that the rumored fourth may be on faith. As a retired pope, Benedict's final encyclical would not carry the weight of the office.
That is something Benedict had not imposed on his previous scholarly works while in office.
"He was careful not to bless his own writings with the papacy," said Pia de Solenni, a moral theologian from Seattle.
When he published books as the pope his byline was "Joseph Ratzinger -- Pope Benedict XVI," de Solenni noted.
"I think he was willing to engage with others." She said his books are "a sharing of ideas and he's putting his ideas out on paper. To me it's an incredible mark of his humility."
One thing for sure: he won't be writing any more tweets. The Vatican said the official Twitter handle @pontifex will be retired along with Benedict.
Life beyond the walls of the Vatican
Benedict said he no longer had the strength to go on. After he announced his retirement, the Vatican said he had begun thinking about leaving the office after a strenuous papal visit barnstorming across Mexico and Cuba.
When he leaves the office he will give up his Fisherman's Ring, which takes its name from St. Peter's occupation. It will be destroyed along with "the lead seal of the pontificate," Vatican spokesman Federico Lombardi said.
He will also be giving up his personal security detail, the 100 to 120 members of the Swiss Guard who are responsible for round-the-clock protection of the pope.
"He received security like any other head of state," former Swiss guard member Andreas Widmer said.