>>504802This. RVs are fucking expensive. A truck camper or tow-trailer would be less expensive, but even then you're looking at probably $5k minimum for anything that isn't a leaky, moldy POS. Plus you'll need a truck.
And don't forget that RVs of any kind have to taxed, licensed and insured. And RV insurance ain't cheap, especially if you intend to live in it full-time.
I'm sure over a long enough time span, it would even out to be cheaper than renting. But the significant up front costs is going to negate any savings you might have over an apartment for just one summer. Unless maybe you're trying to rent an apartment in Manhattan or San Francisco.
Just get a roommate.