There are lots of ways, but no guarantees without spending a bunch of money, which is unlikely to be worth it.  As much as I hate traditional social media, it is a good way to get the information out on this.  Think about places that the well-to-do frequent and see if you can hang flyers at any of those places.  Tell everyone you know to tell anyone they know about it.  I think some grocery stores have a board for flyers.  Are there any big businesses where potential clients might work?  You could ask if you could hang flyers there.   "We can cook for your employees so they can work longer," is a good motivation for the business to allow you to hang flyers.  There also might be some older people who would like the service, so maybe a senior center.