I sub out my fertilization, the company I use is reasonable and I just mark it up 10%. However one of my potential clients didn't like that I couldn't do it because I'm not licensed. Even though I had the low bid when they accepted a more expensive competitors bid because they wanted one contractor for everything. Wasn't a huge loss but 10k accounts don't grow on tree's either...
I know in Ohio if you are any part of the transaction you need to be licensed. I don't think you need to have your company licensed or insured. I would check on that.
Then maybe you could mention if they are cleaning your gutters and fall and injure themselves, they could sue you to cover their medical bills. (Something like this that points out that the person they hired could sue them as well.)
Then at the bottom say something like before you hire any contractor demand to see their proof of insurance and a copy of their license, (if one is needed).
Point out you are licensed and insured and to call you to avoid these headaches.
If you want to add a graphic to your add, you may want to consider this one from the free lawn care flyer section.