Cash and Flow are appropriately both four letter words. And should be banished from any serious investors vocabulary. Im putting on my flame resistant armor now because this is BP heresy right? But hear me out.
The only time cash flow matters as an absolute is if you are living off the income and need to predict your budget. The rest of the time, see below.
As an investor (i.e someone with capital to invest) your job is to allocate your capital in the most efficient manner possible to attain risk adjusted returns according to your goals.
The problem with cash flow is that it is so easily manipulated and so hard to use as a comparative metric that its completely useless for evaluating investments. Increase downpayment, increase mortgage term, reduce interest or go to interest only loans, there are so many ways to manipulate the cash flow. That is why sophisticated and institutional investors (aka people with more money and better math skills, or better accountants) use IRR as a way to compare and evaluate investments.
This takes into account the total return over the period of the investment. It includes sum of cash flows, equity gain and time value of money to generate a real estimate of return. So even negative cash flow properties can have huge positive IRRs and high cash flows can have mediocre IRRs. And IRRs can be compared across investments. You can compare buying bonds or stocks or real estate with each other. And determine the best way to allocate your funds.
Of course there is future gazing involved and assumptions in all of the above but at least you have numbers that may mean something! With is a lot better than c-a-s-h f-l-o-w