I'm just making up numbers but 22% seems a touch random (as a threshold) so maybe he has had specific experience that tells him that's what the proforma needs to show to cover the unexpected.  

Depends how much time and brain power you want to apply.https://www.forbes.com/sites/brettowens/2018/07/29/the-best-reits-paying-up-to-8-youve-never-heard-of/#20b1971d5e3b

NOT fair is to abuse your power as a landlord ("I am going to raise your rent to more than you expected, or take $400 from you, and there's nothing you can do about it").

If you have power and water it wouldn't be too bad. 

Powerful stuff

I got into contract on a another property 2 months later before the other one had sold, and three days before closing I was short 20k unexpectedly not because of illegitimate costs, but because I'm newer to this and I forgot closing costs.

If a customer can get a contractor to front materials and labor , more power to them .  

But its power lies in the fact that you don't have to over pay for a deficient asset just to burn up 1031 funds. 

We do both, and sometime take it in the shorts taking a loss on a sale, and/or covering unexpected costs our clients incur. 

Just something to keep you from going in to more debt if an unexpected expense arises.The next step really depends on your specific situation.