I would try to launch the first version of the product on your free time and take it from there. Take a week of holiday to work full time on it, maybe on a quie

I would try to launch the first version of the product on your free time and take it from there. Take a week of holiday to work full time on it, maybe on a quiet week at work with a holiday on on the middle of the week. With one week full time, you will probably give it a huge boost. This is the least risk path. If your employer is open to unpaid leave, take one month without pay. That goes in a flash at work and its easier to sell to management. With one month of solid work full time on it, you would give it even a further boost, then take it from there depending on the reaction. You mention you are a junior developer. You should likely try to become a freelance with your own company as soon as possible, that would give some funds, equipment and a company. I don't know if that is feasible in your local market or somewhere near.