I bought my bus for 1500,
It's been a long project just taking care of the rust it has. I can show you a few pictures of what we are in the process of doing.
This rust is not near as bad as the one you are looking at.
I work around 70+ hours a week, so this project is months long.
The amount of work that I am putting into this bus is rewarding. I've purchased a ton of new tools and a welder which has also provided a valuable experience.
So for my first bus,
Cheap, a little rust, some new tools, and a vast amount of experience = worth it to me.
That being said, I will never do it again. You can get a rusty bus for cheaper, but your time alone is way more valuable than the money you save. Then you add in the consumables (grinding wheels, cutoff wheels, sanding discs, wire wheels), and all the tools you will either have to buy or ruin by countless hours of use.
Judging by the rust on the outside of your bus, I would guess the frame behind the wheels is in really rough shape.
Good luck with the decision, I hope you find a fruitful project that you will enjoy!