If you are into landscaping a great addition to learn from fundamental aspects would be permaculture principles. You would learn how to work with nature with the goal of creating a renegerative landscape.

Why regerative?

Once you get the system working for itself, you would reduce the need for synthetic inputs to be integrated into your system reducing costs and improving fertility overtime.

You could start collecting byproducts that otherwise would be discarded. You could utilize the byproducts in your lawncare or landscaping business to further create additional biological products that could be offered.

Some options you could create and offer would be fermented plant brews, mulch, compost, biochar ect for local applications.

(Depending on what part of the cycle you harvest and ferment would determine the nutrients you would unlock for applications. Early Veg growth would result in higher in N, Flower / fruit would lean towards higher levels of P and K + in comparison)

All feeding back into increased biology and fertility of your soil. Even at the bare minimum, organisms themselves are comprised of Carbon and Nitrogen. Increasing biology into your soils would ditectly increase carbon in your soil, increasing your carbon credit allocation overtime.

Would the carbon credits make you rich over night? Not unless you scooped up a piece of property with extremely high soil organic matter. Another route would be incorporating the carbon credit allocation as part of your landscape / permaculture buisness model.

Example:

Customer hires you for a landscape job, plan out what your customer wants. Give the option of carbon credit submission and the key selling point to them would be the additional revenue potential they would get from following the regenerative practice. Even a 75% customer / 25% buisness split for carbon credits would seem appetizing compared to 0%. The worst to happen is neither party gains additional funds, the best is you just gained a 25% split based on payout dates. (Yearly payout most likely.)

Soil Organic matter testing is fundamentally simple in the concept. Take a measured amount of soil, heat it up to a specific temperature for a specific time. Once the Organic matter has burned off, measure the remaining amount of your sample and subtract from the original. The difference between the two indicates the amount of Soil Organic matter that you had. Obviously this test isn't going to certified for your credits, things where you would send sample to a certified lab. Buuuuut, you wpuld get a rough idea of what amount your are working with.