Can't afford lessons?

I've had some experience playing piano, I'd say I'm a beginning intermediate. But had to stop because I had to pay it all for myself and it was getting expensive. I started missing it, so I asked my mom if I could start up again and help me by paying for half because I want to progress. She told me to just play my old songs on my own. I don't know what I should do! Lessons kept me motivated to practice. And I can't progress just by playing the same songs over and over again. What should I do?