The plan: I am identifying on/off market properties that are targets, will do all of the real estate work (listing, showing, advertising, vetting, etc) and will split the cost of the purchase of the home and the material costs for any needed repairs.The contractor will be subbing out portions of the job and be on site mostly full time until the project is completed. 

will 3b has a steady market?

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.

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.

I don't know what market your rental is in.

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

@Chris Elliott There are many options left in the market.

Market changes all the time. 

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

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.