I used the proceeds of the primary residence I owned in NC to grow a portfolio of value add buy and hold here in College Station.

Quote from @Meliisa Lee: I recommend splitting the properties or selling them off and splitting the proceeds.

I understand I cannot legally require them to respond, unless the notice specifically requires it, like for instance, a notice of entry, but it's making it difficult to manage the property, and I'm not sure how to proceed.

Terms such as interest rates and payment schedules are typically negotiable.Combining creative financing with seller financing can include strategies like:Subject-to and Seller Financing: Taking over the seller's mortgage and financing the equity portion through the seller.Lease Option: Renting with an option to buy while negotiating seller financing for part of the purchase.Wraparound Mortgage: Keeping the seller's existing loan while they finance a new loan that includes the balance.To proceed, consider connecting with experienced investors, understanding local legal implications, and attending networking events to gather insights.

The bottom line is this: Concealment is not asset protection, proper (time consuming and expensive, I know) management, and good, prudent, practices (ditto), WHICH ARE ADHERED TO, and insurance (expensive), are needed for asset protection.

I know some people do this but proceed with caution.

An agent should be able to send you a estimated proceeds sheet. 

Unfortunately, that is an expensive time-consuming process.

Now let's say one or both people making the purchase owned a condo previously where they roll over the proceeds/equity into the new purchase and put 40% down.

remember, these are NOT conforming loans, so all the consumer protections one might be used to having aren't there.