You have to keep in mind expenses for paying evictions, time when tenant is in house and not paying rent (credit losses), good tenant applicants that can't move in for three more weeks, paying for utilities when house is vacant and making ready, etc.  

From there you can refine your prospecting by using some of those assumptions on properties you don't have the full picture on.For example, as a baseline I use 8-15% of all gross income as my fixed expenses, 10-15% for capital improvements/reserves, 5-10% for vacancy and 1-5% for loss to market.

When they don't pay their bills and the bank was left taking a loss, that money needs to be made up from other people who pay their bills.

Loss of job, medical issues, divorce, something to show that the owner is not going to be able to pay.

This allows for you to contribute all of your cash flow towards the HELOC, thus cancelling interest, and when the cash flow is not there (a vacancy, large repair, etc) you can pull out to cover the loss rather than come out of your own living expenses.Final note: I have yet to meet a single investor who bought there first property with all cash.

Cut you're losses and take action quickly and learn from the experience

I had tenants go to jail and I still got rent and was able to get him out with minimal losses.

If there are losses, they can be deemed as passive losses and unless there is passive income to net them against, those losses stay locked up in the corporation.  

You'll learn about a new expense not mentioned yet "Loss to Lease" when you try to evict and it takes six months.Have you ever heard of the appliance a month plan.

As a general rule, carry the amount of coverage that is relative to what you would do with a property in the event of a "large/catastrophic" loss.