Prince appeared "pale" and "weak" during one of his last public appearances, it has been claimed, amid reports the music superstar stayed awake for 154 hours before his death.
Employees at Electric Fetus record shop in Minneapolis said the musician did not look "in the best shape" when he visited the store five days before he was found at his Paisley Park estate.
Prince's brother-in-law Maurice Phillips reportedly claimed the singer had worked for six days without sleep when friends and family held a private service at the compound on Saturday.
Mr Phillips, who is married to Prince's sister Tyka Nelson, is said to have told fans outside Paisley Park: "He worked 154 hours straight. I was with him just last weekend. He was a good brother-in-law."
Max Timander, who works at Electric Fetus, said Prince visited a day after the Purple Rain star was rushed to hospital when his plane made an emergency landing in Atlanta, Georgia. Celebrity news website TMZ reported that he had overdosed on a painkiller called Percocet at the time.
Mr Timander told the Press Association: "Everyone I've talked to on that Saturday said he looked kind of pale and he was not totally looking in the best shape as he normally is.
"It sounded like he was looking kind of weak. I know he had just got over the flu supposedly."
The mayor of Chanhassen, the city which is home to Paisley Park, said discussions were taking place to stage a public service in honour of Prince in the Minneapolis area.
"It's clear his friends and family would support the idea," Denny Laufenburger said.
A private funeral service at a local church is expected to take place in early May, he added.
Prince was found collapsed in a lift by staff members on Thursday morning, more than 12 hours after he was last seen alive when he was dropped off at Paisley Park. The 57-year-old singer was pronounced dead at the scene.
Police are investigating whether foul play was involved in Prince's death after authorities said they had "no reason to believe" he killed himself and there were "no obvious signs of trauma" on his body.
According to Electric Fetus, the six records bought by Prince during his last visit to the store were Talking Book by Stevie Wonder, The Time Has Come by The Chambers Brothers, Hejira by Joni Mitchell, Inspirational Gospel Classics by Swan Silvertones, The Best Of Missing Persons and Santana IV by Santana.
Mr Timander said: "He was a huge supporter of the store. He bought six CDs, including a Joni Mitchell CD, a new Santana CD and a used Stevie Wonder CD.
"We sold out of everything we had by Prince two hours after his death was announced."
Prince's body has been cremated and the "final storage" of his remains will be private, his publicist Yvette Noel-Schure said.
A cause of death may not be released for several weeks.
Prince's Paisley Park home will be turned into a museum as a lasting memorial for his fans, the star's brother-in-law has said.
Mr Phillips told The Sun: "It would be for the fans. He was all about the fans - this would remember his music, which is his legacy.
"Prince was always private but would have wanted his music remembered."