The girls house

First introduced in Chapter 24 of River Rat, it's a small rental house in an older section of Flagstaff.   It's called "the girls house" to differentiate it from Al's house.

Initially Karin, Crystal and Scooter are living there.

The single-story house really was small, small even for a two-bedroom, but Scooter figured it had to be better than a sixteen-foot travel trailer, and besides, she and Crystal probably wouldn't be there all that much, anyway. Karin had set herself up in one of the bedrooms; in the other one there were two three-quarter beds, all made up.

(Scooter's referring to the travel trailer that she lived in while working at the NOC)

Besides being small, the house has one disadvantage...

Karin tells Crystal and Scooter It only has a tiny water heater and not much water pressure, so while you can have a hot shower, there's no such thing as a long one, or a nice one. You can get a fairly decent tub bath, but I don't think either of you would like those very much.

In Chapter 10 of Growing Together it's referred to as:

The girls house was a small house that Karin, Crystal and Crystal's friend Scooter had lived in before Karin got married. Crystal and Scooter had kept it last summer, if only to have their own beds for three nights between their three week river trips.

Crystal said "It's pretty crowded right now, with Scooter and Jim staying there along with Mary and Dave and us. In fact, Preach and I have been sleeping on Paco pads in the living room."