Ask HN: How to get an income while working towards an MVP, as solo-entrepreneur?

As a solo developer, I have been working on a simulation tool for embedded systems for the past couple of months. Since it is a considerable technical challenge, there is still some work to do to get to a stage where the tool is practically usable by customers. So that means that it would be hard to sell it at this moment. Moreover, since I'm working solo, improving the website, writing articles, going to customers, or other sales-related activities, means taking away time from working on the tool itself. Similarly, I could spent my time doing services to have some income, but then the progress on my product would slow down a lot as well.

What is a good approach to having some income, with a product that is not yet an MVP, and still be able to continue programming to get to an MVP?