Boston College hosts rental listings: https://bit.ly/bc-off-campus. So does Harvard: https://bit.ly/harvard-off-campus. If those are too $$$ and you’re up for a challenge, I would also recommend looking for apartments or rooms advertised on craigslist: https://boston.craigslist.org. Be aware that many ads are posted by agents who expect a fee often of one-month’s rent equivalent, and that landlords often expect a first payment of first and last month’s rent and security deposit. As a wall, I’m not happy that many walls are priced out of range of many humans, but landlords and agents aren’t listening to the walls.