I think you could benefit from joining the local REIA to help get you started and network with other local investors, contractors, syndicators etc.

Start building your real estate team, join if you haven't already a local real estate investing club, watch your market to see what is selling with what features, and track what properties and areas are in demand.

I now want to look into "flipping" new construction or spec home building.

Consists of 3 buildings each different style.   4400mth total rent produced.   400k ask- 1 duplex, 1triplex type homes - 5 doors, really old home (1940ish) currently in C to D condition. 2600 total rent produced, 155k ask- 2 Single family homes - 2 doors, really old home (1940ish) currently in C to D condition. 1800mth produced, 150k ask- 2 Tiny home sheds- 2 doors, 800 total produced mth.  40k ask. 

You will spend 2x as much as you think and it will take 2x as long as you think and you will get 2x fewer permits than you should because you will use 5x the number of contractors you should.You are thinking money first which is why it won't work.

Looking into single family houses or multifamily, as there is an actual land that you own and potentially build ADU/DADU in the foreseeable future.

Either way, I think your first step would be to find your lender, agent, contractor, and property manager you want to work with and get started!

Do we just lower the sale price by equal amount and the contractor will need to take payment from the new owner? 

I did this project from a contractor POV, I did a lot of the work myself.

Building a new duplex to start my real estate career.