Dilemma: My partner is a narcissist how do I move on?

Hi I would love some advice please!!

My partner decided on Boxing Day that he no longer wants to be with me after 17 years. We met when we were 18 and have three children together. He hasn’t given a reason other than he just doesn’t want it anymore, we aren’t married so unsure what my options are. We live in a house owned by his parents so I have no entitlement to this and will have to move out with my children while he stays in the house.

I feel heartbroken- more so for the kids who are going to have their whole lives turned upside down. 
Our relationship got worse over the years, he is a narcissist and has slowly taken everyone out of my life. I have no solid income apart from child benefit as he has always thrived on me being totally dependent on him.  He earns a good wage but is self employed and his income varies from month to month- especially is he takes on ‘cash work’ which I’m thinking he will probably do more now so that his income looks less and will have to contribute less. 

I have nowhere to go, am currently still living at home with him but he’s just out every night doing god knows what and speaking to me like shit. I don’t know what my options are. Where do I go? How do I afford anywhere without a proper income? I’m scared I haven’t been independent since I was 18. 

Any advice would be amazing thankyou x