Does that count as a formal offer ? 

You found the pluses, and you've acknowledged the minuses which are few.Remember to include continuing education - if your state requires it - in the annual costs of your license and MLS access.There are actually classes from the REI education school to which I am connected which count toward a broker's continuing education requirements in IL.

You double counted tax and insurance.

There is not one magic piece, however i can tell you that putting your letterhead on a yellow letter completely defeats the purpose of the yellow letter as @Mitch Messer mentioned.Yellow Letters work great.

@Sean O'GormanYou are right on both counts.

True, but I count on my tenants alot to take care of the unit and call me when there are issues/meet venders.

You'll experience less wear and tear:This is in my own personal experience of hosting over 600 and counting guests... only once have I had to file a claim on a deposit because a guest got into one of my client's liquor cabinets... they were very apologetic, and I could have done a better job of setting ground rules for them.  

My personal recommendation is to self manage first if you have a smaller unit count so you know the ins and outs so when you continue to grow and have to get a property manager you know what it's like and how to best manage the property manager because you have done it before. 

I personally would look at a duplex and see if that would be more feasible since you can qualify for a more expensive house since you can count the other units income.

Wouldn't that count for something in front of a judge.