My customers dont usually want to get involved with mowing. They hire me for that. They just want everything to look good without having to worry about the details. They pay me to worry about the details. If theres a market for that type of service in your area than go for it.
As far as pricing, I always start with basic time and materials. I learned by under pricing and losing money on my first few jobs. Once you get a feel for how long things are going to take, then you can get your pricing figured out.
When it comes to fert pricing, you will need to measure everything. Once you have your square footage, you can figure out your product cost. Then then you should charge a certian fee to cover getting you on the property, and then your time. For me, I never use a straight sqft pricing method, each property is different therefore the prices are different. A property with tons of beds and small strips of grass will take alot longer to treat than a wide open property of the same size.