I ended up having a handful of clients and all of them were older, between 50-70 years of age.Let me suggest you find other ways to reach the same demographic. I assume people aren't mailing you their computer. This sounds like a local business.
Make a list of local senior housing projects, senior centers, etc. Design up a paper flyer and print a few because that's the absolute cheapest way to do local advertising. Go knock on doors and ask if they have a bulletin board and if it would be okay to leave a flyer with them.
Use tear off tabs to both help potential clients retain the contact information and as an informal tracking mechanism. Periodically replace the flyers when the tabs are gone or nearly gone.
Make a list of places that accepted your flyers. Follow up periodically.
Expect your flyer, your contact list and other details to evolve over time. As you hit on some successes, think about which things worked and make some guesses as to why. Ask yourself how you might replicate the piece of the formula that you think worked in order to further improve on what's working.
Then repeat the process of trying a thing, thinking about the results it got and trying to improve on those results.
Was there a book that changed the way you'd market?
Starting in my teens, I read a lot of books and articles over the years and even attended free classes from local Chambers of Commerce. I knew a lot in theory. In practice, I spent a lot of years failing to make money in an entrepreneurial fashion.
While desperately poor, I began collecting recyclables to help cover my expenses. I learned a lot from that.
My background had inculcated me with broken mental models. Merely reading about how you were supposed to do business resulted in me spending years pursuing "window dressing" instead of pursuing customers.
I registered my fictitious business name with the county. I set up a business bank account. I had a spiffy leather briefcase. I said "yes" to a free trial of office equipment I didn't need. I bought a nice desk and office chair.
None of it resulted in paying customers.
There are things that are highly regulated where you absolutely need to jump through the right hoops before you can reach out to your first customer. But if you are doing something that isn't highly regulated, you need to figure out a product or service people will pay for and then find ways to connect to customers.
That's it. That's the crux of it. Then iterate on your successes and view your failures as learning experiences.
If it's regulated, you need to add in some steps to make sure you are in compliance. You always should do a little googling to check pertinent laws for your jurisdiction anytime you try a new thing to make sure you aren't overlooking some legal detail.
So, for example, you sell X locally and you know how to do that successfully. You decide to branch out to online sales. Now you need to research sales tax when selling out of state plus details of shipping.
They both have logistical and legal components. For starters, you should look up if it's even legal to mail it (across state lines, to another country, whatever). It may be perfectly legal to sell locally but illegal to mail it. Some people ship first, learn it's illegal after the fact. Oops.