Ariana and Armando's place is really nice. They were very communicative about check-in and provided really detailed instructions about how to get to the apartment from Termini Station.
The mini-apartment is part of a guest house in a larger building. Basically, you enter the building and go to the second floor. Then you enter the guest house (through a locked door, which provides additional security). The guest house has a few different rooms for rent, including the mini-apartment. Each room has its own key. We were a little surprised by the set up, but everything was very nice and I was happy to have the security of 3 locked doors.
When we checked-in Armando gave us a map and pointed out all of the key places we wanted to visit, including the best times to go to avoid lines. He even texted us info about how to book certain tours! There are also some great restaurants and cafes in the neighborhood, as it's a little removed from the more touristy places.
We were able to walk everywhere we wanted to go from the apartment. Be aware that when you are in Rome it will be a lot of walking! But there are so many cool and interesting things to see along the way, so it's worth it.