Pay Off HELOC or Primary Mortgage?

[Ukaku E.]

Hey there BP Community, I have been investing in real estate for about 5 years and have acquired 5 properties.  A couple of them were house hacked and we currently live a duplex right now and with no out of pocket mortgage payment.

We have the good fortune of having 80K on hand and are contemplating payoff one of our properties that has a 79K primary mortgage while keeping a 25K HELOC balance that is attached to the property.

My question is: Is there any risk we might not be considering regarding paying off a primary mortgage (788/month) when a HELOC (199/month) would then move from secondary position to first position lien - ie loan acceleration, change of terms, etc.

Our goal is to minimize monthly expense while starting up a 3D virtual tour servicing business.

Additionally, any alternative recommendations for the use of above mention funds?

Thank you