You may want to knock off the butchered lawn stuff and yes I know its in the fert company play books to always blame the lawn guys. I have a unethical company in my area that loves to blame us. About 6 years ago I get a call from some one up state says he just sold his company for 4 million dollars and now is going to make a new fertilizer company in my area. He then goes on to tell me and you know it is illegal to apply pesticides with out a license so you will be giving me your fert accounts right? To which I read him my supervisor number my partners supervisor number and my business number. He quickly hung up now when ever I have a lawn that he ferts for I get that bs I even have one of his check lists and half the questions are ways to push the blame on to lawn mowing.
Now as for running full service we do offer it but our fertilizer side is a fraction of the lawn mowing side. What you got going for you is if you are making a living off just applications you have 500 accounts. Which means if you just signed up 20% you have an instant 100 lawn account cutting list. You are going to hate the margins where a fert only guy can bring in 200-300k a year if he has a thick enough list. A lawn crew tends to bring in 55-70k a year per man. Granted they don't have the obscene product costs but they have equipment, trailers, trucks, large amounts of fuel, and as it ages huge repair bills. It is going to be many years before you recoup your investment if ever. And it involves trusting someone to run things that you admit you don't know what your doing. He breaks even 2 days a week, loses money on the 3rd, and makes a modest 5% profit the other 2 days what are you going to do to fix it you won't even know whats wrong. He will tell you we are doing our best and then what? Also fert companies can afford to drive much longer distances because of there small crews often one man. Of my 190 lawn accounts over 150 are in my home town. I keep a very tight rout we drive between the trucks less then 300 miles a week for the lawn list. Now imagine what your crew will need to drive when you ask you client list to let you mow and as is always the case the ones the farthest away all sign up.