There were pros and cons with our stay at Manuel's flat.
The pros are that Manuel's cousin Pierre checked us in and was very flexible with timing which was excellent. They were both communicative and kind. The flat was nice and clean when we arrived and is very reasonably priced and in good proximity to the trains.
The cons were mostly the neighborhood itself. My boyfriend and I arrived at Gare du Nord a little late at night, and the 10 minute walk to the flat was scary for us both. The place was packed and chaotic, we saw what was obviously illegal sales of stolen goods on the sidewalks, and both felt in danger of getting pick-pocketed or purse-slashed. We took cabs back the rest of the trip rather than being on the streets at night. As helpful and nice as Pierre and Manuel were, due to the neighborhood I would not stay here again and I would definitely not stay here as a solo female traveller. The only other con was that the bed was very uncomfortable.
If you feel like you can navigate a seedier part of town, then this place is a good value; if not, I recommend avoiding it.