Tianyu's place was great. I only stayed for a few days, but I still felt that I was very welcome and I liked it a lot. The apartment is in a very nice neighborhood, close to the train that takes you to downtown Boston in only a few minutes and also very close to a wide array of restaurants in Dorchester. The apartment and the guest room are very clean and many facilities like the kitchen and washing machine and a dryer are provided to the guest. Tianyu made sure I felt like I was at home, and was glad to show me parts of Boston and interact with me. He is a very educated and smart person that makes it easy for the guest to conversate with him, and his calm persona is also very nice if you prefer to stick to yourself.
The bed was very comfy, the room is nice, it doesn't get too hot at all, I didn't even need to use the fans provided, though I'm not a spoiled American that's used to 15C inside during desert climate outside.
Generally, I'd give a sixth star if I could. Best wishes to Tianyu.