You just need enough cash to cover anything unexpected or unavoidable.

This is why I love real estate, no other investment vehicle that I know of that allows you to eliminate unavoidable expenses while still making money. 

It will cause unavoidable cost: who will move the fridge?

And to be honest, there could be more but we are trying to be gentle with our tenants and not expose them to too much change too quickly (although some of it is unavoidable).  

Every company will have vacancy and the occasional bad tenant, these risks are unavoidable (not every nightmare tenant is a felon with bad credit, after all), so it's important to take a broad view of user experience and ask about what the company does to minimize the risks where they can.Pay attention to language.

Surprises are still there, it is unavoidable, but being able to look at the two sides of the coin now, we can help the investor prepare for that.In Addition to these tips, I have uploaded some files in the File Place here on BP, that I find it useful to all rehabbers.

@Kodie Altvater costs are ultimately a factor of 2 items, if you're efficient: labor+ materials.the goal is to arrive as close as possible to just those 2 factors with as little add-on as possible. add-on being profit, a companies overhead, etc. labor and materials are unavoidable (as well as other stuff like permits)....so how does one arrive at those costs?

We were nothing less than side-swiped by what's been happening (and having to take a tremendous financial hit), but it's been unavoidable. 

It seems like this is a recurring gag and is almost considered unavoidable amongst some homeowners.

No one wants that, but the question is if it becomes unavoidable?