I've got about $525K in equity in the property, but lenders have told me that I cannot get a HELOC to access that equity for additional purchases because the duplex was financed as an investment - they have said TX law dictates that HELOC can only be used on primary residences.

When this occurs, area incomes fall and cities reduce spending on police and schools.

However, evaluating your sentiment (and your wife's) on that will be important. 

@Arlinda RexhoWhen considering a 32-64 unit multifamily property in Texas, focus on strong locations with population growth, proximity to amenities, and low crime rates.

Spend at least 2 hours per day researching online about your desired investment strategies.

They should be bale to guide you more based on what you are looking for in the area. 

I'd like to know because if they select them as they are entered into their database, right after filing, then there is another good reason to always extend and file on the last day.

Again, the BiggerPockets store has some books on this topic, or you can learn about it by watching podcasts, reading blogs, and interacting on the forum.

I also have a $175,000 line of credit ready if something catastrophic happens.

Please text me with the number on my signature line and can walk you through my configuration.