I'll assume this will be an out-of-pocket new installation, and probably off-grid since you mentioned batteries.
There are hundreds of variables to proposing a system, but every design begins with getting answers to many questions. There isn't enough information here to help with designing a system but you can get a bunch of support on what kind of details need to be collected to start piece it together.
The first approach to an off-grid installation is evaluating loads. Air conditioning is an easy one. You'll find that is is less expensive to replace whatever's installed with ductless multi-zone mini-split high EER system(s) that will give them the ability to exclude uninhabited rooms from being controlled and run at a lower level of energy consumption for the same amount of cooling. The EER rating is key running from PV when you start thinking about how much extra in panels, racking, batteries, inverter capacity, and more you'd have to size for the load. In fact, there are mini-split systems and refrigerators that can be powered directly from the 48V DC bus and batteries which directly reduces the need for inverter capacity. The most efficient units always cost more, but this mindset of prioritizing power consumption efficiency when selecting appliances is a necessary transition to living off-grid. Old refrigerator? Incandescent or compact fluorescent lighting? Get rid! Every light needs to be LED. Identify what's saving money and what's wasting it.
You need to know what the major heating appliances are powered by. Water heater, stove, oven, clothes dryer, and space heating. If any of these are electric they are HUGE loads and need to be addressed individually.
Most people have a budget, so if there is a budget ceiling it is necessary to start with that and work backwards. You need to know if this system needs to be autonomous and fully disconnected from grid power, or if it has grid input capability, and/or if there is a generator available. All of that is relevant in sizing batteries and arrays because what happens when power gets low requires different actions depending on this stuff. It's also necessary to know how critical the reliability is - for example, is there any medical equipment for the residents, a well pump for water, communications hardware that would be needed if there was an emergency. Those factors determine things like what tier of hardware you use, and maybe if a secondary inverter is installed. There is a lot of horribly cheap import equipment out there (confoundingly popular with many on this forum) that takes a lot of troubleshooting, bug and errata mitigation, and vendor patience to get to even a semi-functional level of marginal reliability at best. This location may add a layer of logistical complication that should be considered when proposing gear if reliability is a factor.
You need a site survey, to look at roof-top versus ground-mounts. You've got hurricane and lightning considerations. The equipment itself needs a sheltered place to live - especially the batteries. You're looking at the land, the shading, the direction roofs and clearing are facing. You're also considering where conduit can be run, roof penetrations can be made, PV disconnect, combiner boxes, or maybe trenches for a ground mount system. You need a place for the batteries. It's going to be a lot - probably a whole rack minimum so be thinking 50-60kW/hr. worth. The placement of the inverter is relevant to the main distribution panel, or sub-panel if you have grid power there. Generator considerations, if applicable.
You can also talk about what to do with excess power when the batteries are topped off and the loads are satisfied. These are diversion loads. For example, a second hot water tank with electric heating elements can be installed as a pre-heater to the main tank or tankless water heater. Also, if they're on well-water they can install a water tank that the submersible fills, and then a low-power DC pump to keep the house pressurized and fed separately. The well pump PLC is programmed to keep the tank at low level normally and then fills during solar availability. Water tanks reduce the need for more batteries when off-grid.
This is just a start...
