But how can we draw a line between repairs and replacement?

If the property is bleeding money every year from repairs, maintenance, or turn over you'll never get ahead.You can tap equity with a HELOC (challenging right now), cash-out refinance into a new loan (much higher rates), 1031 exchange, or sell (tax hit) but the numbers and property condition need to guide this decision.

It is almost as hard to buy a fixer upper at a price that will cash flow after repairs. 

Is this a low number for both vacancy and repairs? 

I got free repair estimates (inspections) from two roofing companies.  

Roof was flashed and repaired in May.

Those repairs will never get done.

There has been such a journey with renovations and the person repairing the property, but hey!

So my plan is to use the equity in my own home for the downpayment and for the repairs and take out a conventional mortgage for the house itself.

What’s your definition of an expensive repair?