How do I scale up and on-demand cleaning service mobile app

You need to look at your KPI's. If your acquisition strategy can afford referrals, implement that, and ask your cleaners to spread the word (after they complete a clean) and reward them.

-Sell your mobile solution to a local cleaning companies, like outsource cleaning company, digitize their business and have their clients move to your platform
-Rate cleaners and Rate clients
-Build and in-app incentive for rating system for services rendered
-Allow cleaners to perform extra jobs that is out of their scope to earn more points "incentives" so they can make more money

If you have the supply of cleaners and are just looking for demand in the service on the consumer side but don't want to spend/risk losing money, I'd recommend a commission/affiliate based marketing strategy. This is a full proof way to grow with guaranteed profit without putting dollars at risk. I would have to get more of an understanding of your app, your market, scale, etc but affiliate marketing is one of my areas of expertise and I'd be happy to chat further on how you can do this. https://clarity.fm/stevenkrinberg1/expertise/affiliate-marketing-to-grow-fast-and-profitably

The best way scale up and on-demand cleaning service mobile app will to look at an example of a similar successful app that had captured market for quite a long time. Since you are really worried about the demand side, I believe this link will surely give you an idea about how to do it: https://www.appventurez.com/blog/how-to-make-on-demand-laundry-app-like-cleanly/

Besides if you do have any questions give me a call: https://clarity.fm/joy-brotonath