There are relatively fewer 4 plexes though.  

However, if I do have an unexpected financial need I can just write a check from the HELOC and access those funds immediately.This quick access is where  the danger resides. 

Properties here still cash flow, but they're fewer and further in between.

There are some exceptions (eg own 3 houses or fewer or apt building with 4 units or less and you also live there... be sure to read the laws - this thread and several others give a number of good urls) but yes, generally you have to rent to them and can't reject them due to the service dog.

I look at way fewer numbers when I buy.

If housing market crash, i would lose a lot if not all that and my primary residence will be in "danger".Am i wrong to think this way?

(I know just enough to be dangerous so talk to your tax attorney or CPA)I would rather pay $30k more out of pocket if you truly believe the property to be worth more than appraised.If you plan to 1031 exchange until you die then pony up the $30k you can always refi later to pull that money back out if it really is worth the $370k.

I know there are probably several links out there on BP but I haven't played around with the site enough to be very dangerous.  

That's why these calculations are important.Michael Evans I believe you are accidentally illustrating the point in the danger of isolating a favorite calculation and basing a purchase decision off of that vs taking a few sides and comparing them.

@Bryan Otteson I am not in the business of renting to high risk or dangerous tenants or donating to charities so please keep  your DUI analogies and charitable contributions to a discussion where they are relevant.