When you get near the building, the misc quest to retrieve the key from the Front Desk Attendant will be activated. There are no enemies in the building but there are two Mr. Handy attendants. It's also worth noting that the place has scattered Aluminum cans and some aluminum trays so look carefully on the floor to find them.
On your first visit, talk to the Mr. Handy and say that you're checking in to get Gladys's Room Key. You're free to loot whatever you want inside as well. Take note that after you've explored inside, a group of synths will enter the building and attack the Mr. Handy. They will proceed killing the house cats inside unless you killed them yourselves or protected them from the synth.
In the lobby, there's a book return terminal with no valuable prizes inside. Beside it is a Novice door which has two stimpaks and a jet on the floor by the skeleton. In the counter, there's a Novice terminal you can use to unlock the security door nearby. The security door has several items inside, including a Syringer, and an issue of the Massachusetts Surgical Journal.
Unique safes
Beside the counter, there's a stack of safes which you can't lockpick. Their keys are found inside each resident's room as listed below. Take note that each room has a theme that suits the resident's interests. Also, the safes only contain basic meds so don't expect much. There's a chem station in the kitchen and some aid items in the fridge.
Mortimer (sea): From the lobby, first door to the right along the corridor. The key is on top of a boat model, on a shelf.
Randall (hunting): On the second floor, near the ramp. The key is located on his bed, under the pillow.
Ethel (painting): In the room beside Randall, go through the broken wall. The key is located on the floor, under a paintbrush.
Catherine (cats): This is the room with the house cats. The key is found by the feeding bowls on the floor.
Margaret (plans): Found on the floor, by the bags of fertilizers.
Edward (writing): On the table beside the typewriter
Finally, Gladys's room has a steamer trunk, a usable bed, frag grenades, and army uniform.