The way I see it, you can take the exact same principles and apply it to buying something like a classic car.

So if you wanted to sell the investment after time and use this as your primary & house hacking until ‘dream home’ days, you could sell and pay off the original loan balance and go this route or pay off original loan amount without selling and keeping it and apply for the one time benefit restoration - which is not the same as entitlement re- installment for active/permanent change of station orders or foreclosed upon properties. 

@Chris Collins excellent tips for when applying.

I'd like to create an official rent contract applied to the room they'll be staying in, but want to ensure this is fine within context of the loan (assume primary occupancy still valid since only renting room).

The Rider reads: "This form applies only if form 3522 1/01 are used" (it was).

I'm curious, why didn't you and the tenant apply way before it got to this point? 

We got to the page that says:Due to the number of members in your LLC, you are considered a Multi-Member Limited Liability Company (LLC) as the type of structure applying for an EIN.Since you are a multi-member LLC, we must initially classify you as a partnership.

Triplexes specifically are harder to come by, but your same idea can apply to a duplex or quadplex.To echo a great point though: even if you are not positively cash flowing in year 1 (maybe even 2), you are still DRASTICALLY reducing your monthly payments and saving lots of money a year.

In either scenario, my friend and I would either be applying for a loan together, or I would apply for it under my name only.

Same concept applies here.