You might also consider lenders like Velocity Mortgage or LendingOne, which cater to real estate investors.

Mortgage broker.

It's essentially using multiple novel (but legal) applications of long-standing regs to an activity that largely didn't exist at the time they were created. 

My mortgage and escrow don't allow me to consistently profit enough on both floors to handle a 20% management fee and not take a loss some months.

It felt like a no-brainer for the value of the land, but being able to utilize a traditional mortgage because there was a clean yet simple 3 bed 2 bath house on the lot made the deal even sweeter!

Present the existing tenant a PDF with all of the rental comps and Rentometer printout showing what the market rent is.2.

If you hired out all the work, you are more likely to get ~$0.50 for each dollar you spent on the ADU assuming 1) in single family zoned area 2) not converted from existing habitat space. 

@Kristee BadetHouse hacking involves living in a multi-unit property and renting out others, potentially offsetting mortgage costs and allowing savings for a personal home.

The deal sounds fine overall as long as they are in good shape and you can move and rent them on your existing land, but do you want more mobile homes?

I didn't see where you factored in a $3000 mortgage payment (principal & interest only) in today's higher rate environment.