Get copies of the lease and proof that they are paying on time and yes get an estoppel certificate. 

Proof of his funds updated monthly..

That simply confirmed “proof of concept”.

I would say the cash flow would go up every year and that would usually be the case but my son will be moving into one unit probably for just the labor to rehab the last unit (collected rent will go down for a year).After that rehab is complete, at market rent I would have about $8k/month cash flow with underwriting that most would consider conservative (for example $1200/month allocated to maintenance/cap ex). 

They subtlety put the burden of proof on me to show that my line is capped so my contractor continues to install cleanouts so we can flush and scope- cleanout has to be put on the Water Districts vacant property. 

The claims of 1hr to collect rent, produce receipts, and deposit checks also seems like a reasonable claim if done physically and not electronically.

You can find higher ROI (on paper) here and probably in other cities…but the probability of actually collecting rent significantly decreases.

Simultaneously, develop a detailed scope of work and collect bids from multiple contractors to compare costs and timelines.

If not I would suggest finding a servicer to collect and manage that note. 

As soon as you get the leases signed and proof of security deposit and first months rent deposited into your account your can use it.The question should be, do I even need to get the units leased out to qualify ?