Similar to you, I'm thinking about other strategies for off-market leads and tried direct mailers, but not sure how effective that is for multifamily.

You might be able to get a better yield by finding a value-add project or a BRRR type property, but the market rate stabilized is 4-6% probably.Just be careful of insurance right now, it's been going up and seems to have stabilized, but it's still all over the map depending on the specific property and who is doing the insurance.

will 3b has a steady market?

Setting up networks of agents, contractors, and wholesalers in various markets. 

In 2018 we began sourcing off market deals by doing direct mail marketing campaigns.

Madison has a fantastic LTR and MTR market.

In the NJ market how likely is cashflow in the first two years?

Here’s our OPINION for the Metro Detroit market (use as a template for your target area!)

But this could also vary in your market, for example if inventory is so low then buyers may offer to pay your closing costs too. 

I will be charging this RE investment company (again an RE company that I own 50% of) market interest rates.