Welcome to the forum from extreme Eastern Va. Yeah the only way to check the hot water heater would be to fill it, turn it on and see if it heats up, then drain it after. As with any used RV, look for any signs of leaks inside the unit and check the roof/sealant condition. Also check the floor for soft spots. Since that is a hybrid, give the bunk doors/seals and tentage a good look over as well.
2017 Coachmen Catalina 283RKS
2018 Ford F250 Super Duty 6.2l CCSB
2010 Jayflight 28BHS (sold)