If this was a rental some commcercial lenders or asset based lenders could be do a cash out on the property as long as the rental income covers the debt service and they won't even look at your personal income.

Can't believe your partners allowed the tenants to move in without being screened...

His screening came back with only previous addresses.  

Not only just for qualifying for loans, but for covering the unknowns that come up with owning and buying RE.

I could preach about tenant screening, but my tenant was inherited, so I frankly didn't do any - but would if I had to get another.

What are the most important points to cover ?

Youll have to check if they cover the areas you're looking at.

@Ben Narro     In California, some of the credit unions offer RV loans that should cover a tiny home on wheels.

We can not give you more advice outside of our area as our insurance does not cover them.

Purchase price: $340,000 Our 5th unit, single family home zoned for secondary suite.I will be covering this unit into an up and down duplex.