Mobile homes and tiny houses are great options for housing but they have little or no room inside to accomodate a traditional pressure tank. A pressure tank typically holds 30-50 gallons of water under pressure by means of a sealed air bladder. A pressure switch senses a drop in line pressure after some use and will turn on the well to refill it
The well driller has three options; they can place a traditional pressure tank in an underground vault (good) or they can place a special small tank in the casing (bad). The third expensive option is to install a VFD well control that requires a very small pressure tank
The in the casing tank is always the easiest solution but almost always takes up the entire casing and prohibits the installation of any type of hand pump. If you do not have a underground vault or a Variable Frequency Drive (VFD) well control or you do not know where your pressure tank is, then it is probably in your well. A call to the well driller or investigation with a flashlight is required.
Find a neighbor with a compatable well and strike a deal
Rework the well to remove the pressure tank and install it in an underground pit
Drill a new well (not as expensive as you might think since you dont need trenching, pump, pressure tank and you only have to hit water and go another 20ft or so
Rain water collection or generator
Well with a in the casing pressure tank