to step away from "guns" for SHTF, you and your father might want to do the easy thing 1st and evaluate your disaster preparedness for earthquake, flood, fire, tornado, power/water/waste disruption, logistics (food, fuel, toiletries, et c) disruption before considering armaments. that being said, securing a home against robbery with sound structure, locks, windows, doors, a simple sensor-based security system with alarm are all very affordable and less legally and socially dubious standards that you can get a lot of help with from many sources, and even get discounts on services or subsidies to be brought up to your local codes. safe storage for valuables and legal (titles, deeds, certificates, permits, et c) documents, et c
after all that, a handgun for the night stand and/or rifle if you want longer engagement ranges can be considered. a stolen or rusted out weapon or corroded ammunition doesn't do anyone any favors.