We did over 70 F&Fs during the 2009-2011 time frame and did well.

But you do have a time frame (usually 21 days from the execution date) to receive a "yes" or "no" from your lender. 

There's a lot more that could be said about how to structure the note, the time frame, interest rate, payment structure, etc.

This will require compliance with all building codes which will not be inexpensive.

I am now wondering if there is a difference in expenses.

The contract likely has a timeframe in which the seller agrees to order the HOA resale package documents (typically a couple of days from accepted offer).

This means knowing if you will attempt to cure other defaults, time frames for other foreclosure actions, or just letting it go to foreclosure ( this will likely lose people money unless if they purchased a very small HOA lien )Not sure if a non-borrower, but owner has any right to redemption if a redemption period exits.Does this home have equity or is it upside down?

That huge time frame exists in theory, but not in reality, due to the many limitations imposed.

In what time frame? 

Here it is:20% for profit10% for sales costs like holding cost (2-3%), real estate commissions (5-6%) and closing costs (1-2%)total: 30%Deduct from 100% and viola - there's the basis of your 70% rule.For houses below $70K, your expenses like closing costs specially in expensive states like IL, can eat up a higher percentage of the ARV/ sales price.