In the great depression, stocks declined about 89%.

You might have candy for diabetics, that is low calorie, might have some fruit treat that is even healthy.Not so much about candy stores, but what is your business ethic?

I've tried submitting a seller financing offer for the aforementioned duplex but they declined. 

It is unlikely that the real estate market in the valley will decline by 25% so you will probably not be upside down or at risk of losing your properties at any point in time.

I would advise getting that HELOC ASAP as the market may start to decline, so you want to maximize the highest equity you can get now.

In 2009 it was very challenging to get a loan on most RE sectors and that spiraled the decline in pricing even further.

As soon as I offer proof you decline lol.

And if/when rates go up, property values tend to stagnate or decline anyway...It sounds like you are also only considering conventional financing.

Considering decades of decline in US manufacturing, this doesn't seem to bode well for future growth.Thomas S. puts it more bluntly than I have, but he's right.

me personally I think that the retail business is going to slowly decline over the next decades because as prices rise due to inflation and the rising operating costs- means tenets will no longer be able to keep the operation open due to the constant decressing rates of return for business's.