Stefania's apartment is a good value proposition.
My wife and I walked from the metro station "Re Di Roma". It took about 10 minutes or so with the help of Google maps on my phone.
The host is amazing and super helpful. Check in was a breeze and flexible. We settled in quickly.
The apartment is spacious for a studio apartment and had everything we needed for a multiple day stay. It was very clean and had plenty of natural light. It is on the lower ground floor so would be great for the hotter months to keep cool in but would be cold in winter. 2 aircon/heater units are available for use. The bathroom was also generously sized and well presented.
The location is about a 10-12 minute walk from 2 Metro stations. There is a bus stop that is very close that you can catch a bus into town. The Colosseum can be reached by foot but will take about 35 minutes which we did. It is about a 10 minute walk to Archbasilica of St. John Lateran.
The bed is a fold away type. The mattress is a little thin so the supports underneath can stick into the hips a little so your sleeping placement is key. Small and light folks won't have a problem.
External factors:
A consideration is that most dwellings have tiled flooring. This is great for cleaning but is also a great conductor of vibrational noise. Very light sleepers may have some trouble with the neighbour above wearing high heels walking around and shifting furniture at night for extended periods.