I want to know if  there is a high demand and if homes are renting easily.  

We advise landlords to require two main criteria:1) Household income should be at least 40x the monthly rent.2) Applicants must have a credit score of 680 or higher.It's also important to review credit reports for red flags like rental collections or high credit card balances.

It's high risk potentially not so high reward situation. 

Unit A is about 100 years old and Unit B is almost completely new.Pros:-The duplex is in a very desirable neighborhood with home value appreciation year over year at about 50+%-Rent is also in high demand within this area-Cash flows well even with high interest rates and increasing property taxes-Home is price below average cost per sq ft-The house has been renovated and some parts of it has been remodeledCons:-All issues are with Unit A, the 100 year old unit.

even with a lower purchase price that's probably 1/3 of DC's they still mostly still don't work - rents not high enough, too much deferred maintenance, not in the right location, or all of the above. 

Unfortunately, this is near impossible without selling the property, rates are up and are likely staying high. 

. $140 equity in our primary residence that we’d be open to getting a HELOC on (would love feedback on if people recommend this or not).Given our limited available resources for down payment, high home prices, and higher interest rates, is now a bad time for first time investors to enter the market?

That banana republic management approach to the economy has caused high interest rates.3.

The $200k makes no sense and I highly doubt that buyer closes on it. 

Any learning material link/book/video I can go through to learn more about them?