Use this partnership to ask questions and talk strategy about where you want to end up in the future as an investor.

As for getting a HELOC, it's prime + index (fluctuates based on the market), so to answer your question, if you are able to qualify by yourself, then it's always a better option to get a loan solo, then use your spouse's income as a backup for future investments. 

mortgage principal will remain in the future

I would gladly invest with them again in the future!

Let me know what you end up doing, seems like he has a bright future.  

Save for future expenses, especially if self-employed6.

Just make sure the grass doesn't just look greener before jumping.  

They remain available to assist investors throughout the investment lifecycle, whether it involves refinancing options, addressing financial concerns, or facilitating future funding needs.

I hope to talk to or run into any of you in the future.

Most likely you will regret selling your duplex in the future, so seldom sell and try to find a way to keep it.