If you sell, will you invest the proceeds in something else for example the stock market?

If they close and sign up with us then we do a site walk etc and begin onboarding.I am also a broker who assists in finding the property, doing walkthroughs etc and I get paid a commission at closing from seller.Long story short I would expect them to give you an analysis of properties you are interested in for free based on the hopes of future business, if you want them to go above and beyond and attend showings etc then ask them if they are interested and offer them compensation for their time :)

I would consider partnerships in the future.

Investing outside of real estate: What other investment opportunities (stocks, REITs, or businesses) might make more sense in such a market?

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

Also, the historical data tells me that 3 years of underperformance means that future performance must improve substantially in order to meet the IRR goal for the investment.

Any advice on how to get rental income reported (from the current rental property and future income from renting out our primary residence) and lower the DTI??

Quote from @Ryan Smith: Hi everyone,With what's happening in the stock and securities market, now is the best time for many passive investors. 

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. 

So, every non-government job your tenants have will end in the foreseeable future unless new companies move into the city and create replacement jobs that pay similar wages and require similar skills; Otherwise, soon all that will be left are lower-paying service sector jobs.