I usually run my math by running what if scenarios of a 10 or 30% decline in rent and my ability to sustain in an environment.

Until you get established, your personal income is going to need to sustain the debt service on the rentals.

If I still cash flow ($100+/month) then I feel good about it sustaining long term.

The flooring damage was sustained during this past winter season with rain/snow.

In fact, I would just include a line item in my project budget as a cost to the project.From your perspective, I'm not sure how sustainable charging only $69 to $99 / month is for unlimited design services especially for clients that are doing several flips per month.   

The owners of 100+ units can sustain and adjust since they knew at purchase this was a possibility.The new entrant to the MF space (possibly from BP since, along with the gospel of Cash Flow, another often repeated never questioned manta is that SFRs are a stepping stone to multi families) who has a few 5 or 10 plexes didn't underwrite the deal thoroughly, assumed rent growth keeping pace with expenses, and equal entrance and exit cap rates will feel the most pain. 

I have heard metrics of 6 months housing supply, 5% interest rates, and sustainable 3-4% home price appreciation, but have you ever seen/lived through a "normal" market?

I will probably be somewhere in Asia or Africa building sustainable homes for the poor because I would have made some serious millions while in my twenties. 

It's no longer sustainable or a good use of my time while trying to grow other aspects of our business.Thoughts or experiences welcome!

North Park, South Park, and the other areas surrounding Balboa have properties that will do well for you as a STR, but are much more reasonably sustained if you were forced to transition to longer-term tenants.Let’s get together while you’re in town to further discuss the current market dynamics and take a look at a few properties that will work with your goals/level of risk aversion.