You need a license to apply a PESTICIDE.
You can apply fertilizer, seed, lime, etc. without a license.
My suggestion is to establish a relationship with a local LCO who can perfrom all your fertilizer/pesticide applications for you.
Then you can begin offering the service for your customers and offer them full service.
For the next few years, you can observe/learn/study the application business and take the necessary tests to obtain your license.
THEN you can step in and run that part of your business properly.