I've done dozens of renovations now and I still use the 20% buffer and because of that I'm typically able to come in at or below my budget.  

Adding PM cost into the calculation to give some buffer is probably smart.

The equity created will give you a good buffer during these uncertain financial times. 

This is a common issue, but having stricter cost control measures or a contingency buffer in place could help on future projects.

Only able to do this with a rehab to force appreciation and buffer the value?

But your own psychology and mindset does matter, and investing in real estate, while not making us wealthy, did give us this back-up plan where we knew we'd always have a roof over our heads and enough of a financial buffer we could figure something else out.

Waiting for up to $30k offers more options and a financial buffer.

Good idea on having a buffer saved up.

If this is someone you and/or a member of your family might be dealing with in the future it may be smart to have someone as a buffer. 

Find that number out first and try to give yourself a buffer since cost of living will still go up but also will your rents and expenses.