I found an inexpensive one acre property with an old manufactured home in Willamette County, Oregon. I want to buy the property with my daughter (co-sign) so I (she, as co-owner and future occupant of the primary/man unit) can put an ADU on the property. (Local laws require one of the units be owner-occupied.) The idea is to consider the single-wide as the "primary" unit (that's how it's being sold) and apply for a construction loan to finance both the primary unit (the man home) and the future ADU. The question is: can it be done?

As long as you own the land and there is no HOA it should be possible

Look up your local zoning ordinances, the ADU might have to be smaller sq ft than the main house

www.hausable.com

Thank you! Yes, I think the ADU will be 400 square feet: the manufactured home is 816 square feet.

I agree with the zoning, especially pay attention to the allowed kitchen size. I'm not sure what county you actually mean by Willamette County (assuming you meant our Willamette Valley, which is made up of several counties) but I looked into this in Clackamas county recently and the kitchen size allowed in a 600 sq ft ADU on a 5 acre lot didn't really allow for a fully functional kitchen, more of a kitchenette or maybe motor home sized appliances. So something to watch out for.