We had a great stay at Paulo's apartment. It's a cute small old house fully renovated, with a cozy attic bedroom (beware if you're tall, I did bump my head a couple of times!). The space is more than enough for two, and having two bathrooms I can see it working for four, although in that case maybe better if you just plan to come to sleep and not spend a ton of time hanging out in the flat. The kitchenware available is pretty basic but enough to fix a simple meal.
I think the location is pretty good, close to Santa Apolonia station were you can get the metro, train and buses. We actually walked to reach downtown most of the time. It's also very close to the centre of the Alfama district. The building is in a small pedestrian staircase alley between two streets, we found it very quiet both during the day and at night. We liked being close to the main touristic areas but just far enough so it was nice and quiet outside. The house is kind of boxed in between bigger buildings, so don't expect special views, but we were surprised to have plenty of natural light in the morning.
Paulo was extremely fast and clear when communicating and was very accommodating in our time of arrival at night which was super convenient for us, greatly appreciated. Worth noting that the apartment has a lot of fire safety equipment, and all switches are very clearly labelled which we found very helpful.
In summary, I fully recommend this apartment for anyone looking to spend a few days in Lisboa, great value and nice host.