That’s why Tonnetta Graham keeps a map in her office that shows the tide of gentrification coming up from Brewerytown and Center City. Graham, the head of the Strawberry Mansion Community Development Corporation, tells neighbors they used to be up to their ankles in gentrification, and now they’re up to their knees. There are “We Buy Houses for Cash” signs plastering every pole, and handwritten ones in people’s mailboxes. She encourages people to hang on — to be part of the progress.