I don’t see anything glaringly wrong with their concept but 2 things have caused a red light.  1.

If it's a QM you won't be able to close in a business entity like a LLC, although in some cases you can transfer into an LLC after closing.

Even though your Realtor might be good and helpful their ultimate goal is to get the house sold and no one will see the vision you have set for yourself, in the same light that you will.

I don't know about other areas in TX, but I keep a close eye on Austin-SAN corridor, and I'm familiar with the market in Kyle, New Braunfels and NE San Antonio.

The replacement cost (cost to rebuild, not the value of the property) data providers are pegging the quadplex at close to $2M and most 1-4 unit rental property insurance programs tap out at $1-1.5M before you'd end up in a commercial insurance product.

Radiant heat is what you feel when you sit too close to a campfire.

Did you guys close and everything go smooth?

Assume for a moment its close to max tax bracket ie. nearly 49% (Federal + State), roughly $17K.

You won't find anything close to the Austin market with that budget. 

Very close to two college campuses and downtown.