If you want to start up a co-hosting business, look at as you would any other business.
Do your market research. How does the market operate. What experience do you have as a co-host? What can you offer that is different/better than your many competitors?
Put together a business plan and a marketing plan to identify how you will market your business to your potential customers @Luz561
In the meantime if you don't have experience then consider working for a larger property management business for STRs to get experience.