You’ll want to make sure the rental income comfortably covers the new mortgage, taxes, insurance, and any maintenance costs.

Would you be able to rent for cheaper if you didn't have the property?

We are looking into houses on the lower end of the scale at first to get started for a "low risk" (we could pay mortgage out of pocket no problem even if property is vacant for 30 years) house that will give us the experience we need as rental home landlords - and I am looking down the road at potential investment ideas to keep this thing rolling.

Mortgage balances go down and eventually get paid off. 

Is it better to have a mortgage on a rental or a primary? 

If the rent payment covers your mortgage and you have a good tenant, why would you get rid of them to take on the expense of unit turnover, because you will have to do one, and the 5% vacancy loss just to increase your rent $150 per month?

Imagine a $185K income earner ($100K after tax) having a $600K mortgage.

Many banks handling tax escrow accounts for mortgages have mistakenly thought there was one tax due twice/year or totally missed one of the taxes.Investors should research the SEV and the Non-Homestead property tax millage rates to project what the property taxes will be after adjustment.

In addition our healthy balance sheet allows us to pre buy mortgages down to as low 3.75% for our buyers, most builders can not qualify to do this.

I second @John Underwood and @Bruce Woodruffs comments.Get it up, make it a little cheaper and see how it goes.