This place simply fits my bills:
under $100 per night
no pet
safe neighborhood
near subway station
on-site washer & dryer
working desk & chair
comfortable bed
stable wifi
smart TV
I felt safe walking at night. Lots of restaurants and supermarkets nearby. Other guests in the building were respectful in keeping the bathroom and common area clean. Despite the fact that the bathroom is shared, it was always available for me. Please be aware that the bedroom is opposite to the park and you could hear kids shouting and playing basketball all day. This might be worth noting for light sleepers.
The host was always very helpful and responsive. Check-in and check-out time was flexible too. I will stay here again whenever I am in Boston.