need licence first then:

from chatgpt
Bus purchase $10k–$40k
Mechanical repairs / tyres / rego $10k–$40k
Demolition + insulation $5k–$15k
Interior (walls, bed, kitchen, shower, $15k–$60k
Plumbing + water tanks $5k–$15k
Electrical wiring $5k–$15k
Solar panels $6k–$20k
Lithium battery bank $10k–$40k
Large inverter + chargers $3k–$10k
Air conditioning / diesel heater $3k–$12k