If I would have used competent management, the manager that I picked and vetted, then it would have cash flowed, assuming they could have filled the vacancies.The big lesson I learned is that the property manager selected can make or break a deal. 

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

I have not selected a specific property yet, but want to at least identify my potential investors.

What kind of account or vehicle would you suggest to start saving down payment money for my first rental property?

Come up with terms (Down Payment, Interest Rate, and Amortization Schedule) such as a 5% Down Payment, a 6% Interest Rate, and 30 Year Amortization Schedule.

The maximum fixed-rate period seems to be seven years, and there is generally a balloon payment at 10 or 15 years.

When we moved our companies to a new accounting software we looked at Quickbooks, but found its international awareness (tax rules, multi-currency, locale support, etc), project/job, and multi-company abilities to be clunky.To be fair, none of the candidates hit everything on our wishlist.We ended-up selecting MoneyWorks by Cognito and have been satisfied with it over the past three years.

For example, the buyer, if they find problems with the property or stop making payments, can blow up the seller's credit.

If you sell, you could access the equity you’ve built and put it toward other investments or save for a future down payment.

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.