We wanted additional units to pay mortgage and have cash flow.

Best to call city hall for the town you are buying in to see what if any rent control rules are in place. see link below if you require additional information and call the Jersey City Landlord Tenant relations office. https://www.jerseycitynj.gov/cityhall/HousingAndDevelopment/...Jersey City CPI chart on recommended rent increases: https://cdnsm5-hosted.civiclive.com/UserFiles/Servers/Server...The state with the highest eviction rate in the country right now is South Carolina. 

.- Value add - How much does it cost to build additional storage units?

In addition to these you can find information about appreciation.Many of the people recommending expensive properties are doing so because of appreciation.

If you want to add it to places like affordablehousing.com then that gives you more exposure.  

These are professionals with additional training and a stricter code of ethics.

If you do call them best case scenario you get the listing, sell their home and end up with some additional buyer clients that did not end up buying this particular house.

I used the 75% rule on the income and added it and my DTI without the rental goes from 24% to 38%.Or does it just allow me to just take the net profit of that rental and add it to my rental? 

If you are looking to refinance the rate and aren't concerned with taking additional equity out on your property, then you should use a rate/term refinance.

IMO this is much too little additional return to put your personal residence at risk.