I just see it like a co-signer on a residential loan, just different term (maybe even slightly different conditions since it’s non-residential).  

My plan is to use an FHA loan with a co-signer to increase my odds of being accepted.

It seems like the only way for me to be pre approved for a property in these areas is to have a co-signer on my loan due to how expensive they are and my current income.

Myself, I would like to invest in MHP or multifamily as a CO-GP ideally with an experienced investor.

I'd consider it with double the deposit, good income, and a co-signer.

Basically the duplex is for her but she would not qualify for a loan herself so I would be a co-borrower. 

Since it sounds like you're on the fence with this potential renter, ask them if they can get a co-signer.

Under a co-tenancy clause, a tenant may have the ability to exercise specific remedies if the property’s occupancy drops below a certain percentage or if an anchor tenant is no longer operating at the center.

I've definitely settled on the house hacking strategy, and with the lack of multifamily inventory it looks like it will be a co-living situation.

@Adam Elbary If they are signing on the loan, they would be considered a co-borrower because they would be on the hook for the loan as well and it would allow you claim to be an experienced investor as a team.