A lower down payment decreases your cash flow (because you'll be paying a larger mortgage payment), but ties up less of your capital which you may be able to deploy elsewhere.

The moment you want to sell any loan at a premium, your chances of selling to someone in the industry significantly decreases.

Also, if you plan on living in one of the units you could look into FHA loans to further decrease the down payment you would have to pay.  

Anyone looking at your books might want to know why you suddenly decreased that units rent by $200 per month. 

I’m guessing the lender will only take into account the decreased expense of the 4 units?

When credit dried up and property values decreased, those people were suddenly underwater and on their way to insolvency. 

More media exposure, HGTV, etc have increased the demand of "why don't I try that" people so prices on active markets have increased so it appears margins are decreasing. 

I understand their property values decrease, but do their tenants all of the sudden stop paying rent? 

We're at that time of the year where prices are going to be decreasing over the next few months, not increasing.

In our county the taxes jump substantially the year following the purchases, but then only like 1 1/2% per year after that until a fair value assessment is reached and then slight decreases every year after that.