There is no such absolute rule or mandate for REI - it is up to you on your comfort level with your cash flow versus total investment versus appreciation potential.If I followed that rule, I would have missed out on a LOT of great opportunities over the years.We bought a house in Jones Valley in 2017 with negative cash flow - why? 

Where I live, we still have a severe shortage of homes--median time on market is still 7 days and it would likely be shorter if not for delayed negations being the norm. 

May negative cashflow until fixed.3) Buy established business: assuming you mean something other than real estate related.

But I will be honest, the rentals I have been added the last 2 years here in DFW have negative cashflowed.

As the investor gains experience, they are not only able to more successfully foresee the “bumps” along the way, able to handle recessions, temporary negative cash flow, unforeseen capital expenditures without panicking, but will also recognize the opportunities necessary to turn a loss into a break even.

For this deal to work under those conditions, the purchase price would need to be closer to $179k.With your original assumptions 249k, the deal is marginally acceptable but not great, given the negative cash flow in the early years.

I think you've forgotten about the concept of Constructive Receipt. 

I love this concept of a developer working directly with a rural municipality to build affordable housing.

To me that is negative cash-flow, because I include hard and soft expenses. 

(I know a lot of investors who are doing this, but I've been surprised to find out that it's a new concept that others haven't considered.)The more units, the better in this scenario because you can hedge your bets with more units.