I work in Public Safety and we have conducted numerous search and rescue missions.
Here are some things you might want to take into consideration.
If you plan to have a fleet of sUAS use the same brand. Live Streaming for us is very important as this allows stakeholders not on scene a way to participate. Both Autel (Should be up and running by now but might not be) and DJI (FLight Hub 2) have a cloud based service that lets you coordinate multiple drones and live stream. We use Flight Hub 2 and the live streaming works great, it we also get a map with the position of the drones, pilots and telemetry. You can also draw shapes of areas on the map that the pilots can see allowing for hands free flight assignments. It also has an option to make live maps as the drone flies and this gives current conditions.
You most likely want a drone with an IP rating so you have resistance to dust and water.
As mentioned thermal imaging is a must.
You want a camera with zoom capabilities.
You must have enough batteries where you will be able to charge them fast enough and have spares to keep the drone in the air for extended operations.
If your SAR is on call think about having at least one set of batteries always charged so the drone can be deployed without a battery charging delay. This will have that battery (set) have a shortened lifespan so budget accordingly.
You will need a way to charge batteries in remote areas. Plan one or more of: generator, power bank , vehicle inverter. Make sure you know the wattage of these items so they can support all of your electronics.
Buy enough SD cards and portable drives to store your data, and have a laptop so you can store data and use your SAR software like FLight Hub 2 and also to help live stream.
Use the flight logs from all drones on scene and import them into a master map (cloud based) so that all parties can see what areas have been searched. Not doing so allows for areas to be searched repeatedly or not at all.
You will mostlikely need portable radios.
Have multiple people trained to prevent pilot fatigue. All members of an sUAS team should be able to fill any flight crew function and have rest breaks.
Ensure you have a way to connect to the internet. (Not always possible). THe internet is needed for live streaming, cloud master search map and communications.
In New Jersey SAR/Cal Topo is the software of choice right now for public safety agencies. If lets us show all areas searched and other valuable information.
Know the limitations of a drone in SAR. SAR needs terrestrial assets just as much as aerail. Assign the correct asset to search the correct terrain. A well conducted SAR will use drones, vehicles, people on foot and dogs. All of these assets can be equipped with apps on phones, collars on dogs, and other software that will allow for live views on maps or the downloading of the areas they searched. With this information you can now see a clear picture of what has been searched and what has not.
Drones are not a magic bullet in SAR, they are another tool. There is training that must be conducted and they must be used in conjunction with other assets. Do not force the drone to search an area that it is not suited for.