I stayed at Mark's place for about a month.
Mark's place is cozy and clean, just as shown in the photos. It has all the amenities for a great medium to long term stay. Mark was very accommodating and communicative. I had a last minute flight change, and Mark was able to accommodate me without issues. He also provided information about things to do and places to see in Rio.
The apt is located near Posto 2 in Copacabana. There is a drug store, ATM, grocery store and even a dentist just a block away. The area itself is fine but I advise caution especially at night (even moreso if you're new to South America). In general, Copa is not the best part of Rio, but it is the most fun, and that often attracts bad actors.
Mark also ensured the place is comfortable and convenient. For example, the place has multiple wireless charging stations, a printer, a computer monitor (for those who work remotely), a battery recharge station, an air fryer, and even an automatic floor vaccum. You could certainly live without these, but they are there, and it's the thought that counts.
However, WiFi was a bit spotty. It was fine for the most part, but I have to mention it for those that find this important. I don't believe this is due to the unit, but the service provider. I mentioned it to Mark during checkout and it was taken into consideration.
Overall, I greatly enjoyed my stay here; Mark was a great host. I would be back if I'm in Rio again!