You will want to perform a proper dry out of all materials and replace as needed, treat the area and have the lid put back together of the downstairs unit.

You can reduce this risk by purchasing materials and then paying the contractor in increments.

Many insurers have started slipping in language that excludes certain coverages on roofing material. 

Although I rarely watch any of the gurus promotionial materials these days, the 40k flip program caught my attention enough to watch the pitch, especially when I saw him mentioning N.E.

I am very handy so would do any upgrades and he would pay for materials.

Then you need to materially participate in the activity, here are the tests to meet MP: https://www.investopedia.com/terms/m/material-participation-...I recommend tracking your hourly diligently in a material participation time log.

The costs involved are about $100.000 all in (permits, engineering, architects labor , materials ) - I’m thinking that would be a better long term Investment than another SFH . 

In this case, the material cost AND install costs will vary, so having an idea before you even meet the contractor is important.  

I am assuming you would be paying for materials and replacement appliances, etc... so $1000 per month for labor to take care of 5 mobile homes should be seriously looked at down the road.

Zoning, subcontractors, mother nature, P/I during construction and rent up, your loan doesn't get "fixed" until after construction, material inflation, etc, etc, etc.You have taken most of the risk off the table with family financing and family construction.