None because I would crash and burn from the very beginning.

@Robert M Ericksonnon owner helocs are tough to find after the mortgage markets crashed.

It could certainly effect the refi amount and might be a deal breaker where it crashes and burns. 

@Ryan Dossey  If you approach someone who has lived in a house for thirty years who heard of the RE crash and thinks their property is not worth much and you play on that to get a lower price then you might be on the border of theft, morally if not legally.

I think I have a local seller interested in me putting together a lease option /rent to own deal  where I get fee out of 1st option consideration for putting the deal together [wholesale lease option]He wants to walk away with 200K .I told him I coud probably get him 210 to 215K at the end of a 24 month lease period.Here what stumped me He says " Yeah thats fine if the market appreciates ,the buyer will love it,,but what if theres another crash ?

I guess no one could have predicted the housing price crash that happened. 

The supply of homes for sale is super tight, and prices are back to, or above, pre-crash pricing already.

I currently have one 4-family property and I used to own a second that I thankfully dumped right before the financial crash (and it lost half its value).

A few percent might be normal due to building crashing years back but high single digits to double digits shows a deeper problem on the micro level where the property is located.  

I am interested in learning because I wanted to see how much actual rents dropped in different areas during the market crash a few years back.