The average vacancy rate in Austin, TX is currently hovering around 15%.

The tough part about what you are talking about is that rates on a primary home are better than rates on INV properties.  5.75% is a great primary rate (especially right now). 

I'm from CA and I decided to get started out of state (IN and OK) where pricing was more accessible.

Yes, this.The best way not to lose money on a home in Colorado or anywhere ... is to not sell it when you haven't gained enough equity yet.We're keeping everything we can for now.

I’m very content and happy where I’m at right now but would eventually like to move back to that neighborhood as both my aging parents live there.

I have 40 units now and it was the best choice I ever made. 

Although this is technically inaccurate (I saw a case where a sheriff sale of this sort was challenged and the challenge lawsuit took 11 months, deed recording came after that), that is the typical practical waiting period to get the title insurance for the resale.Whatever the mortgage balance, that’s now your obligation to get paid off; before even bidding on any sheriff sale property you should have a good idea of any remaining mortgage balance(s).

Our question is, once we do this, how do we recoup enough funds to purchase a second property sooner than a few years from now?

I house hacked my way into my first rental property this past year and now manage the rental myself. 

My advice is educate yourself by learning online and connecting with multiple of investors willing to give you tips. $20,000 is way too expensive in my opinion.