The ones who only do one or the other are typically members of a large real estate teams which have very particular advantages and very particular disadvantages as well.

I want to help new investors but I am at a disadvantage in this market as it is newer to me than where our current business resides in buffalo. 

But in the next breath you mention all the disadvantages to apts vs SFR in a university town and I would throw out that a third path might be to leverage your property with the greatest equity and use the refi to purchase 3rd SFR staying with the model you know and like.Success is determined by your parameters alone.  

Are there any other disadvantages that I may not be aware of besides the obvious i.e. no chance at bargaining for reduced fees on multiple properties?

They are operating at a disadvantage, especially if the market takes a downward turn and they have to begin offering concessions.  

There are advantages and disadvantages that come with having your license.

It has definitely benefitted me on several levels, but it can also be a disadvantage as well. 

Obviously, cash flow is normally better on older properties but they come with some inherent disadvantages in my opinion.

This is one the biggest disadvantages of living in California.

The disadvantages are that cash flow may be tight to start, because you're paying on your LOC as well as any additional mortgages.