The supply of rentals would be impacted, but the final impact will depend on the local market.

I realize now that I should have supplied numbers initially- for numbers I am looking for $650k and under.

The money that you end up owing to repay the loan over the 5 year term is now post income tax money unlike how you traditionally are supplying your 401k with pre-tax money.  

To create rental income that enables financial freedom, you need a location that meets specific criteria.Rents increase faster than inflation: Prices and rents are driven by the imbalance between demand and supply.

I keep hearing that costs of labor and supplies are rising (when aren't they?)

If you find someone that will let you supply the materials and work for labor only and sign a contract you supplied , you have hired an employee , a laborer , not a contractor .

So Supply and demand have really shifted quickly. 

The process went smoothly, and I’m happy I got a tenant so fast, but the high supply of new builds in the area makes me nervous.

Your property manager should be supplying monthly reports and year end PnL reports that you give directly to your CPA. 

Atlanta MSA is great and growing, but Multi-Family supply coming on line there both now and through next year is significant, wouldn't this be a better/cheaper deal 1 year from now?