These are professionals with additional training and a stricter code of ethics.

It will be difficult to get top dollar for the large house when everything around it is renting for cheaper.

I suspect you could add a second unit for $20,000 - $30,000 which is cheaper than buying another property.

They charge me a flat 6% of the gross collected rent with no additional fees such as what you've listed in your post; with the exception that I reimburse them for advertising when there's a vacancy.

again, I'm just starting out and have a great opportunity, but need additional funding in order to invest.

One mode of thinking is that the cheaper rentals suffer less from a downturn, since "they gotta live somewhere" and some renters from the higher end units will move down until the economy rebounds. 

These are professionals with additional training and a stricter code of ethics.

Additional question, Do I have to change the name on the deed of my rental units to the business name as the owner?

In addition to abstraction we also match the property to assessor records, parcel maps, demographics data, etc.

If any move out I’ll need to make some improvements to get market rates, about $4500 per unit for the cheaper two.