Belem is an extremely kind and thoughtful host. She will give you an overall view of Lisbon and some very useful tips as to where to go and what to see. The flat is shared with other guests, beside yours, there are 3 other rooms with guests. My experience was that most of the time people are out and with two bathrooms with toilets and showers there's hardly ever a struggle to use the bathroom. The kitchen is big and has all you need, we were comfortable in cooking our own meals and having breakfast on the roof terrace in the morning. The room was tidy, pleasant, well lit and has a roller blind. The door is lockable and the bed, although a bit squeaky, is quite comfortable and of course clean. Belem will also give you a very detailed introduction of how to use the flat properly, which proved to me how seriously she takes care of the place.
If I had to name some negative aspects then only that the doors are quite loud when opening and closing them, which might disturb you or other guests.
But all in all this is a prefect place for open minded people to stay in lisbon, we stayed a week and could have easily spent another.
The flat is a 5 min walk from the next metro station which brings you into the action within 15 min. If you're staying in the centre later than 01:00 am (metro closes at 1) I'd recommend a taxi. You can also walk there within 30-40 min from Baixa Chiado.
The area is quiet in the evenings but if you have look around you'll find quite a few bars and restaurants to visit and it seems that this is an area where th locals rather hang around and spend a nice evening out, away from the busy tourist places like Barrio Alto.
I strongly recommend you explore as much as you can and give the place around the main Tourist areas a visit to and Belem has a lot of info of markets, POIs and general accessibility within the city.
For young people exploring the city, this place is perfect!