Since creating this post, I've discovered that there are four siblings... one is willing to move forward with opening succession (estate/probate), but the other three have chosen not to do so - they are fearful of being stuck with unknown "debt". 

The appreciation on this duplex has been enough to be able to retire (or supplement a deadbeat siblings "retirement").  

. * Some of her siblings have good credit and would be interested in putting their name on a property/financing/lease, as the husband provides guaranteed cash flow anyway, but they are not familiar with the whole process * One sister who works as a property manager and has access to MLS, but she hasn't been on that job for long enough to understand REOs, owner financing etc.She is currently looking to rent a two bed at 1,300 USD per month with a 12 month lease in these Michigan areas: *Dearborn*Dearborn Heights*Sterling Heights*Garden CityShe said Detroit only if close to the above (so not ghetto).But at that price I feel she ought to find a property to buy instead.

To do that for your sibling, why not?

Will have to pay sibling half of the appraisal and overwhelmed with the work needed.

I was wondering if it is legal to have a sibling do a mortgage application with me and my wife as a "co-borrower"  as a primary resident and use that to our advantage for lower rates and down payments for a rental.

This is the only paperwork ever filed and the siblings, children are also deceased by doing my due diligence.

Lucky it's just one other sibling.

The opportunity is an inherited property with 3 siblings involved in the sale. 

I will also ask her to keep my number on hand in case the conversation comes up with the siblings soon.