And for the evidence, I would guess that they'll want to see some evidence of the income from the rental days.

Keep in mind that you will probably be required to sign a personal guarantee of the loans.

Hopefully that upfront diligence plus a healthy contingency budget would suffice to keep me out of that scenario, otherwise I would foresee a guaranteed loss, or underperformance at the very least.

The park owner will want a bullet proof guarantee that the home will look great when completed and you will be on the hook for the space rent as negotiated until it sells. 

-- Also, if they are really pushing this as a benefit, what type of guarantee are they willing to offer to back it up?

I guarantee virtually no one is meeting that rule in SD because they're all on here looking to buy in Cleveland or Detroit because in that market price to rent ratios are so askew that buying at a 50% discount probably doesn't get you the 1% rule. 

I guarantee it won't catch anything.

(Manhattan condo starts at 2M) I can guarantee 95% properties are running illegally. 

Yes, it will delay your taxes on this income for another year. 

Sometimes paying a premium on a home also guarantees a higher demand in the neighborhood and with that may come a higher demand for a rental as well.