It is called a Pre-Seed investment and it happens very often. However you need to win the trust of the potential investor. This is done by validating and forecasting your solution (as mentioned before). Previous working expiriens, learned skills, deeper market understanding and so will also add to the trust an investor will have.

Its all about convincing the investor. I think an angle investor is the most likely to invest. Funds will expect more quantitative data and results.