This has to do mainly with the timing of property tax payments for your own home (not for your investment properties) and your charitable donations.

A HELOC could help temporarily if you plan to payoff the balance quickly and are planning to save on monthly payments in the short term.  

I would keep the property and eventually refi to help get your payment down lower.

You should always look for Tax-Deferred and Tax-free methods to Invest.

Interest payments hit my account as expected.

Then Joe sends a letter to Bob and says I bought your mortgage make payments to me.

We were discussing options for payment as we don’t have a lot of capital at the moment, however they have a property that has a bit of equity we could tap into, but they already have a favorable interest rate.

Often times when a builder/buyer moves too fast, or is too busy and overlooks a key piece of due diligence, the unethical ones will try the "scorched earth" method and blame everyone but themselves, even when they know it was their own mistake, and they'll see if they can scare you, the seller, the title company et al into paying damages/fixing their problem. 

Or like your plan use it all as a down payment on a much larger property.  4.

This has to do mainly with the timing of property tax payments for your own home (not for your investment properties) and your charitable donations.