Really funny well done episode.
A nice apartment in Mary's building becomes vacant. It is too expensive for Mary, and Mary and Rhoda don't want to ruin a friendship by sharing. They also discover, in a funny scene, that Lars and Phyllis manage the building (badly).
Unfortunately Ted learns of the vacancy and wants to move in. He soon has plans for Mary to drive him to work and for Mary and Rhoda to take his phone messages and do his ironing and sewing repairs.
There's a great scene where everyone piles into Lou's office for the reading of the lease with Ted's lawyer - a college kid. Ted quibbles with Phyllis about rent and clauses while Lou uses cunning to discourage the move as Mary doesn't want Ted there.
There's an unusual opening scene focused on Mary's neighbour Yvonne (Barbara Gardner) who's vacating the apartment. I guess that bit covered all the required back-story. She's almost like a trial run for the later Sherry played by the superb Barbara Colby.