When running a business you look at all avenues of income: boarding, lessons, shows, clinics, etc. These all are part of your accounts receivable.
You also look at all avenues of expense: materials, labor, taxes, insurance, utilities, etc. These are all part of your accounts payable.
You should make a spread sheet for both columns and see what is the final balance. The hard part is when you have a business that is also your hobby. Some folks like to remove certain aspects from the accounts payable because they would be “paying for it anyway”. In a true sense of running a business you would not do that, but I understand the rationale behind it, and why folks do it.
Remember there are tons of things you cannot account for either in accounts payable (for some reason it never works the other way around…there is never extra income, just extra expenses!!!). For example, I run my own small animal hospital and my autoclave just broke last month. Cost me $700 to fix it. I could not have known that expense, but always keep a cushion for these things. You should do that too…a fence will need repair, a water line bust, a leak, a tractor break down, a tree fall that needs to be removed, etc. I add 10% to my A/P each month to account for those items.