I believe that is going to vary from market to market.

I've heard varying opinions, some people say don't worry about bad credit in low income areas/some say you need to a little bit.

Many ask and are told it is a good idea to rent their personal home, I believe it is vary rarely a good idea.I prefer to invest where my money will earn it's keep.

And at the vary least you have a heloc available for emergency fund to keep your property whole.  

You still have to research the sponsor fees (they vary a lot!)

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Seasoning requirements could vary between institutions.

You can use a  Monthly Rent/Purchase Price (1-2%) as @Jason V. suggested and that is not a bad place to start but it doesn't take expenses into account which can vary widely (insurance, taxes, maintenance costs on older properties, utilities, etc).  

Brian Varmuza the answer will vary by market but in general, the hotter the market, the fewer the contingencies (including financing contingency).

Strategies can vary based on market opportunity, investor goals and simply investor preferences (regardless of returns)...lots of successful approaches.