I am curious if I should analyze this property as a normal multifamily, in the sense that I should consider a split multifamily with 3 separate houses to be the same as one building with 4 units inside.

Yes, building has a floor plan that allows spaces to be split easily.8.

We can do ADU's here, but in most zoning categories they can not be split through the planning dept and sold separately.  

Investor is willing to continue using his money and giving me a 50% split, however, he is wanting a minimum profit of 10k immediately upon sale.

My first broker demanded that I pay her a commission split on a property that I bought personally that was for sale by owner.  

Some give great training programs, others have better commission splits, some may be more investor-friendly, or you might have a good local office.  

Once you start building it up you can split some money into buy and hold rentals.

You can always switch after the training, of the broker split is not good. 

You might want to see about a lot split for duplexes as a fourplex will bust the cap on loans.

If that's not your cup of tea, There's still Manor, Buda, Round Rock, or even San Marcos and many other tertiary markets before you have to go all the way to San Antonio.I've never rented to military people, but I have been a military renter, so I'll give you this word of caution: are you familiar with what renting to a college student is like?