The deduction is optimized as values increase and can potentially offset the entire net investment (including down payment) for high wage earners.

Low or no down, seller financing and low or no interest with a balloon payment later is the holy grail (location, building condition, market also matter but it sounds like you have all that).

But, the self-sufficiency test for FHA loans can be really difficult in SF, meaning that the market rent from units you will not occupy must be sufficient to pay for the mortgage payment. 

Honestly is better spent as a down payment on a second building. 

Best practice is to keep one or two payments in reserve from the buyers down payment for such instances.

If you're a single mom with student loans, a car payment, and living paycheck-to-paycheck, then $20,000 would be devastating and a reserve is critical.

Find Brandon's videos on YouTube for the "four square" method of analyzing homes and practice.

DSCR loans are based off of down payment, credit score and either actual or market rents so it helps to supercharge an investor's real estate goals and net worth.

You can allocate those proceeds any way you want - as equal down payments or buy one for cash and others with loans - It doesn't matter a bit as long as you use all of the cash and purchase at least as much as you sell. 

I offered them 10% down, interest rates favorable to me, amortized for 30 years, but with a balloon payment after 3-5 years.