This may help some but this will depend on your experience with construction and relaying various repairs and renovation items.

With a value of $120k, the only viable option is buying as a rental, depending on condition and expenses.

Depending on what the city would say. 

The answers to your questions depend on your goals.

It depends on the loan product offered by the lender. 

Most likely it will be state dependent and different states with different responses which just turns this into a fiasco

I'm in the market depending on location. 

Depending on your approval, you can use some of the duplex income to qualify for a larger amount to buy the duplex and there are several that show up between the 500 and 1 million mark all around Denver. 

All depends on the terms ($15k spread out over 20-30 years at low interest is like $50 per month)  If it doesn’t affect the CF much, then who cares- it’s still a deal!

The financing isn't necessarily crafty unless you're hoping for very little money down - otherwise it is a standard commercial loan where rate/LTV will depend on the park, your experience, and credit.You'll want to know pad rental $, # pads, paved or gravel roads, size of park, and a few pictures will help us (or anyone) determine your best options.