You’ll want to look at expenses that others have mentioned such as pass through entity tax, education, networking, any start up costs, etc.  

My son currently lives in the townhouse b/c he is going to school and works in the area.Since he is young and starting out in life, I would like for him to only cover the basic costs (taxes, HOA, utilities) just enough for me to break even (I believe that will put him slightly little lower than market rent rates). 

As a result, inventory levels have remained historically low, particularly in markets where demand is high.

Again, it depends on the borrower's priorities (time / energy / fees / opportunity cost of finding new deals / etc)4.

The newest outdoor is still advertising 1st month free as they haven't filled up, and I spoke with the climate controlled owner/builder yesterday (he's a pretty big REI in the area), and he made it sound like he hadn't leased a single climate controlled unit since they opened a few weeks ago.I recently purchased a 140x45 warehouse with low ceilings and had debated doing self storage, but my market seems very saturated.

Funny enough, I was going to suggest you move out of SF due to the high cost ;-) I'd suggest going down the SF condo route to start as financing for commercial units is a lot more difficult than residential properties.

To me at my current knowledge level, this deal only works if taking over the loan - to limit the out of pocket money to acquire the property since the outside reno and new septic would take up the bulk of rehab costs. 

You would need an extremely high grossing property under market value on a something like a 5 year lease to profit, and you probably will not profit after startup costs until Year 2 or 3.Do not even think of trying it with 1/2 bedroom apartments or condos nor 2/3 bedroom homes. 

The bank will put a hold on them, so you can't just draw them out, so don't plan to need them for a while.This will cost you an appraisal on both properties to be performed by that lender. 

DSCR could be a good option if you are refinancing quickly and if the value is higher than your cost basis.