Why did Kev abandon a working business plan?

The cleaning business seemed like a solid idea and was shown to actually be working. But because Kev encounters ONE guy who offers to pay him to move his van, he decides to completely abandon the cleaning business in favor of this new van parking one even though Kev has no way of knowing if other people would actually pay him to move his van or for that matter how much they'd pay him. It's such an unstable business plan that might work fine as a side-business to the cleaning business, but to make it the main business is ridiculously stupid.