If I were to receive a loan from any one of the recommended sources, such as private loans, hard money, seller financing, etc, for property that I want to rehabilitate and then rent; while I am rehabbing and placing the property on the market, how likely am I able to be granted the permission to defer payments for the loan until I get tenants?

This is one of my favorite features of Bigger Pockets especially for asking specific questions.

You will have to pay the money back no matter what source of funds you use (lender or HELOC).Also a partner is the most expensive option.

Aside from the value of the information here, if nothing else it's a great source of inspiration for me to come back to.I'm mostly focusing on single family (if multi comes up I'll happily look at it but it tends to go high - feeding frenzy - in my market).

I would choose a 2nd or 3rd tier city or suburb just outside a 1st tier city (but not the boonies), which has some of the same desirable features as a 1st tier city but isn't yet teaming with investors.

This is one of my favorite features of Bigger Pockets especially for asking specific questions.

For those who have a primary source of income that can support the debt, a loan might still be possible. 

This is one of my favorite features of Bigger Pockets especially for asking specific questions.

Some traditional sources of funding include; business loans, loans from friends, mortgages or secured transactions on assets you already own, saving up money from your own income, starting a non-profit and getting grants from the government, etc.

Another good way to research questions is to use the search feature to find previous threads that discussed those issues.