While I'm a long way from an expert on the AZ/CA area, I did find the La Paz County Park
just north of Parker, AZ an inexpensive location. Water & Electric with a $10.00 pump out service. By the day, week, or month (by the month requires paying for electricity). Bathrooms with hot showers throughout the park & a bar next door with lunch & dinner specials that are pretty good. The bar floats on the Colorado River & some of the sites are on the river as well.
If you purchase an LTVA pass ($180.00 for September through April or $40.00 for 2 weeks & renewable as often as you need) you can stay at a number of campgrounds throughout the southern AZ/CA areas. Some have dump stations, water fill stations & most have dumpsters for trash. Info about the LTVA
. My favorite LTVA is the Imperial Dam area just across the Colorado River in California. Nothing near by; Yuma is 30 miles southwest.