Not sure what the restrictions are over in TX but for Seattle, WA homeowners can build ADU and DADU within the house and backyard they have so try checking your zoning of your house and see what is the max limit you can build.

If you think about it, these approval slots really belong to everyone, so in truth a waiting list isn't really fair to those waiting. 

We also use other options like houses that have ADU/DADU potential.

40 cats and a slot on the local news 😒

I tried to use mine in the photo slot on BP but couldn't per rules.

For my first investment, I'm thinking of building a DADU (detached additional dwelling unit) on my property, and then rent out the DADU on airbnb.

These properties do NOT count towards your 10 slots either.At the end of the day, these loans are not typically meant to be stayed in long term. 

What I did early on that helped is I would install a drop box or mail slot in a closet for rent.

Push the master key tool in the slot you will hear a click.  

I was looking for something that would give me slots for three things: Labor Cost.