"RV" is what Americans call a recreational vehicle — the same thing a German would call a Wohnmobil, a Frenchman a camping-car, and a Briton a motorhome. In the US the word covers everything from a compact camper van to a 12-metre Class A coach. Strong RV rental supply in LA metro. Class B/C campervans most popular for first-time travelers. Easy onward routes to Joshua Tree, Sequoia, Yosemite, San Francisco.
When you book, confirm three things in writing: (1) the depot address and pickup hours (some close early on Sundays and major holidays), (2) the included mileage cap and per-mile overage rate (overage rates of 35 to 75 cents per mile are common, and they add up fast on long American distances), and (3) the generator usage policy if your rig has one — some companies meter generator hours separately from mileage.
Bring your passport, your home-country driving licence (in roman characters), and the credit card used for booking. An International Driving Permit (IDP) is not legally required in most US states for short-term visitors with a valid home-country licence in English (or accompanied by a translation), but a few states recommend it. Carry your IDP if you have one — it is cheap insurance against confusion at a roadside stop.