I'm just yanking your chain.
Just start writing down everything you see that costs money to operate an airplane in a spreadsheet. Start with obvious stuff, fuel, oil, oil filters, etc.
Now factor in the engine overhaul/replacement.
Them's your biggest ones right there. The old saw is if you're not liquid enough to replace the engine tomorrow, don't bother. It can happen. Likely? No. But if it does, the airplane is sitting without an engine with nothing coming in to pay the fixed bills.
(Watched three co-owners do that with a 182. It took them three years to decide to sell the airplane to one of the co-owners who then dropped significant money into it to get it airworthy because after sitting there for three years, it had other things go bad including the bladder tanks.)
Find out the going rate for shop labor and then how many hours things take.
Think about all the items on the aircraft that time out. Mags, vacuum pumps, prop, etc. Get prices on those.
Now from there let the mind wander... Oil filters eh, hmm, there's probably an air filter on this thing. How often does that need changed? A little Googling for prices. Other filters? Avionics filters?
Landing lights. They burn out. How often and how much $?
How long until it needs upholstery? New plastic?
This can go on a while. But on an aircraft as simple as a Skyhawk, the numbers can be found. The trick is not to try to convince yourself that only one or two of those things will happen. Plan for worst-case... if this is a business.
Better... Ask someone else with the exact same aircraft on a leaseback or that owns one, if they'll share their numbers with you.
Our aircraft costs significantly more than one of the rental 182s on the field and about the same as another. I suspect the low cost one has maintenance items that aren't getting done that I wouldn't fly.