And do you find they are more income producing than smaller multi family units (under 4 units)?

@James PetersonThere really isn't anything a lender can do for this type of property if the zoning is "legal, non-conforming" and you can't produce a 100% rebuild letter. 

The excavating contractor company, which did all the remediation work, produced a PA Unregulated Heating OilStorage Tank Closure Report to show that the work is completed and met the state requirement.

My mortgage will be roughy1,900 (going w ho5 home owners) fha report states after considering the rental market in south New Jersey that the effective gross income is roughly 29,070 after operating expenses it could produce a income of 20-25k annually.

Great transition as in income producing property and guest house.

However if the ADU appraises for close to its cost, then the cash flow will quickly nullify the negative position and from that point forward the cash flow is producing actual return. 

Do not be surprised if there is still more that you will need to produce.  

I would argue that the manufactured homes being built as an industry have a substantially better build quality than most of the small companies producing tiny homes. 

Worst case scenario is you rent the home out after you leave in 3 years and you have an income producing property.

The process for a property to be accepted into a voucher program can take months, and during that time the property is vacant and producing no income.