Congratulations on the entrepreneurial spirit it takes to start a business. The better you can demonstrate the outcome from their investment, the less of a risk you'll be perceived to be.

The best way to find any money for investment is to anchor the costs of the investment against the financial upside.

Without directly answering your question of where to find the funding, I would say this: the clearer the path to that estimated 120K of revenue, the less expensive it it to find someone with the 40K to help you kickstart.

Sounds like you're well on the way to validating your idea.