Bottom line: this place is good enough for Lassen travel, but not top of the list.
We were a family of 2+2, and the house could fit 4 people with enough space, hot showers every night, and spacious kitchen. With that, it needs a serious update. Specifically, there were two things that really bothered us: Internet connection was *very* spotty. I know this is a remote area, but this was weak even compared to the area. The connection was completely unreliable, which is an essential these days. Second, after a few days of using the water in our water-bags, we noticed strange yellow color in it. We don't know if it's good or bad (could be something natural), however we wish our kids wouldn't have drink that.
Walter was very friendly. He made a human error about the dates on the first night of our arrival, which caused us to go and find a motel in a small town at 9PM, however made an honest attempt to fix it ASAP, and came personally to help with cleaning the place. The surroundings of the house are very nice, with a large area for kids to run around, deer visiting, and a nice pond. We had everything we need, but- again, it's pretty dated (e.g. the kitchen utensils/amenities, the BBQ etc.). If you plan on spending most of your day hiking in Lassen area this is definitely good enough.