@Troy S.I have some cash, a shitload of drive, 6 years of construction management experience with a top GC, a year of sales experience with a top Equipment Rental Company, a RE license in MA, a few residential deals under my belt and common sense.

Probably depends on your strategy and how well any of those scenarios fit into it. 

You would both be tenants in common and if one of you dies your share should go to that surviving spouse.

No legal advice given... confirm how this fits with the instant scenario.

Your dilemma is common, and fed by the fact that the Solo 401(k) is often over-hyped. 

- Does anyone use a specific application/lease only for these scenarios?

We did a total renovation - New TPO roof, New Windows, New Plumbing, New Electrical, New Base Board Heat, New Window Units, LVP flooring in the common area, Sanded and Painted Hardwood floors in the units, New Kitchens and bath for each unit.

I disagree that the 1065 would be the more complicated route.Relying on each owner to report, accurately, their share of rental activity on Schedule E, plus issuing 1098s to the parties not named in the mortgage would be more complicated and more prone to error, especially if it's being undertaken in a DIY manner..I concede a 1065 would be more expensive than DIY tenants in common, however it frees up the owners to pursue higher value activities and provides them greater assurance everything is being done as accurately as possible.If we want to say error is being mitigated by a tax pro doing the returns of the owners in a TIC situation, sure we can say and all agree to that, but IMO the compliance fees for a pro in this situation for all individuals would be higher than that of just engaging a pro for one 1065.

Worse case scenario, you get 10-20 dead leads that you can put into some sort of follow-up funnel.

@Ashish Acharya addressed this scenario.