Hi & welcome to the site! If this idea isn't it, keep thinking and trying, and never lose that entrepreneurial spirit! Some random thoughts...
Landscaping assistance is about the very last thing people choose to spend on, so you'll need to target people who could afford everything else, and want a nice looking yard, but just don't want to do the yard work or are too busy or infirm - and don't already have a regular service that does everything including mowing.
I believe this group is out there, I have a friend who has a nice one-person little business this way. I think all of her clients are referrals. It's not something that can scale into being the owner of something with employees because people who know enough to do this don't need you to be their boss. Some people will pay someone to plant cute little fru fru flowers in their flower bed, rake their leaves. But they expect a lot for the $.
Your potential customers might be spread around, &/or unlikely to respond to the solicitations of strangers. I think most people are just annoyed when they find random solicitations on their home or worse, under car windshield wiper. The advice to find people to recommend you is excellent. Double that for me.
I think you'll have fewer people interested in paying by the hour, but if you price per job, people will know what they're getting and how much it will be. They don't care how long you spend doing it, and everybody knows people work more slowly when being paid by the hour. People who are paying by the hour will expect to watch you grinding @ full speed the entire time and won't feel good about watching you stop to catch your breath or drink some water.
