You must must disclose to the seller everything including that you are selling it to someone else and how much money you are selling it to that end buyer.

Not if you buy the worst lot with the slowest selling model.

I don't have to rehab before I sell to the tenant buyer, they do all of the work.

The seller will end up with $35,000 less because the agent did not understand the market or the process of selling.

The options are, demo the lot, split the lot and then sell 2 lots to the builder or build myself.

You must be licensed in the state you want to buy/sell.

@Chris KittleI was not directing it to you but many vendors push elaborate schemes and use fear tactics to sell some of these strategies.  

In the webinar, he stated he's been buying/selling MHP for over 5yrs and just recently he and his partners started the investment group. 

That’s great advice Taz, I’m currently working on saving enough money to get started, house hacking is hard for me at the moment because I just bought a house 2 years ago, I would have to sell my house(which is in a great neighborhood great location) and use that money to fund the duplex which isn’t totally out of the question, I would like to keep the house if possible but also would like to get real estate investing more.

You are unlikely to sell all the properties to one buyer.