I've been saying this for a few years now...there is no money in writing novels any more. The best you can hope for is a little extra pocket money or enough to subsidize your writing hobby. Poets have accepted this decades ago. You can count on your fingers the number of people who make a living as poets. But people still write poetry, publish poetry and value poetry. So it has become with novels. There are a few who are best sellers, but that is the same category of profession as lottery winners, and has nothing to do with you or your writing. That doesn't make the novel less valuable in the other sense. Just because we live in a capitalist society that measures value in $, you don't have to get sucked into that. Write the novel for self-fulfilment and for your readers and for your contribution to the cultural conversation that is literature. But don't ask me how to 'turn professional' how to make a living at this because that job category has been in decline since the invention of television, and was killed by the invention of the internet and social media. But you don't have to be a professional writer to be a great writer and to have appreciative readers.