How to access equity for HELOC on MFR duplex in TX?

Hi everyone,

I own a cash-flowing duplex in Austin, TX, that I bought 8 years ago when rates were considerably lower than they are today. 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.

I don't want to refinance because my current rate is under 5% and doing so ruins the cash flow I've got right now. (gross rents $4900; 8% PM; mortgage+insur+taxes = $3600/mo). How do I access a portion of that equity to fund the purchase of 1-2 more MFR properties in more affordable markets like OH, IN, MI, PA, TN, or AL?