Congrats on your new-to-you RV!
Check each of the mechanical systems. Furnace, water heater (both DC and propane), ACs, DC water pump, etc. If you have power tongue and stabilizing jacks, check those as well. Visually inspect all of the water connections you can see.
And check the tires, tire pressure, brakes, and suspension. Lots of folks forget about these.
There's a PDI checklist under the Documents tab that can fill in many more items to check.
Jeff & Laurie -- Full timing in Rockport, Texas
Auggie (our beer-loving English Cocker Spaniel)
Angus (55 pounds of attitude in a 5 pound chihuahua body)
Our home base -- 2018 Grand Design Solitude 375RES -- The "Uno Mas!"
The mobile office -- 2016 Crossroads Hill Country HCT26RB -- The "Poquito Mas!"
Gone but not forgotten: 2015 Heartland Landmark 365 Key West (lost to Hurricane Harvey)