Some TMNT stuff was always meant for grownups.
In the Mirage TMNT continuity, Second Time Around is a Brooklyn building owned by April O'Neil. It is an antiques store April owns and operates. Her apartment occupies the rest of the building from the second floor up.
The building was formerly a grocery store before Mr. O'Neil, April's father, bought out the business and transformed it into an antiques shop named Second Time Around. Besides a large sales room the shop has a side room, a former cooling chamber, which now serves as a storage space for the shop. The rest of the building above the ground floor became the family's apartment where the O'Neil parents would live with their daughters April and Robyn. The basement contained some of the family's storage, and also served as Mr. O'Neil's art studio.
As time went on, April's mother passed away, her father became chronically ill and relocated to a nursing home, and Robyn moved out on her own to Los Angeles, leaving April alone in the building she had grown up in. April went to work with Baxter Stockman as an assistant at his company, and the antiques store was closed.
In volume 1 issue 2, April discovers Baxter is actually a depraved sociopathic mad scientist, and her new turtle friends help stop him, though at the cost of her job working with him. In issue 3, the turtles discover their lair destroyed and their father Hamato Splinter missing, and April invites the four brothers to live in her apartment. Splinter is soon recovered from TCRI and joins his sons at April's apartment in issue 7.
The antiques shop is reopened to provide April a source of income, and April rents out part of the basement to Kirby, an artist who befriends Donatello in Kirby and the Warp Crystal before disappearing.
In What Goes Around... ...Comes Around!, April, Splinter and the turtles are celebrating their second Christmas in their shared apartment as an improvised family. Leonardo is outside the building, but finds himself attacked by the Foot Clan led by a recently resurrected clone of the Shredder. Leo is brutally defeated at the Shredder's hands, and his injured body thrown through the window of April's apartment in the middle of Christmas holiday preparations. What immediately follows is a massive home invasion of the Second Time Around building by the Foot Clan in Silent Partner, immediately forcing the family to fight and flee for their lives. They are saved by Raphael's new friend Casey Jones as the building catches fire. Casey spirits the group to safety outside the city as April's childhood home goes up in flames behind her.
The burned-out shell of the building is revisited in City at War, Part 10 of 13. April and Robyn's father has passed away, and the sisters visit the building's exterior. It has been condemned by the city, but has not yet been torn down because of legal complications. Secretly, inside, Karai and her new turtle allies prepare for the arrival of the Shredder Elites whose former Foot Clan factions have been embroiling the city in a massive gang war. Karai convinces one of the Elites to commit seppuku and die with honor, but the rest fight back, and Karai and the turtles are forced to kill them one by one inside the building's charred remains.
The building is not revisited in the future, presumingly having been demolished. But in volume 4 issue 22, April has recruited Renet to help her solve the mystery of odd discrepancies found in old family albums recovered from the building's basement. Going back in time but inhabiting the bodies of cockroaches, April and Renet observe and learn the truth the Second Time Around building had long been hiding—April was never born as a human child, but instead had been drawn to life using the very same supernatural warp crystal Kirby would discover in the basement years later.