As leasing rates slow at luxury apartment developments in Baltimore, perks like one and two months free rent and even a cruise are being tendered as a way to lure new tenants.

“Offering 2 months free on select units,” reads an internet advertisement for Porter Street Apartments, a new development in Locust Point off of Key Highway.

The bonanza is good for renters and temporarily painful for developers, some experts say, as an overstock of multi-family units in Baltimore that tops 15,000 units over…