What do you mean by "budget"? Is that the cost of the bus, plus improvements? Or is that just the cost of the bus?
If it's just the cost of a bus... oh hell yah!
If it's the cost of the bus, PLUS improvements, then... you will need to be very creative and shop at thrift stores, scrap yards, and the dump, or like to live very spartan.
Living spartan isn't actually a bad idea as it gives you time to decide what you really NEED, versus what you really WANT.