It's the conclusion you came to before you wrote the post I know but bringing up the challenges might make you realize that you might have to offer a heck of a good deal to attract a potential partner.

There are alternatives rather than become a squatter and not pay and screw the landlords who work hard for their money / keep.

Should I rather go look for other cash flow positive alternatives at this time?

Alternatively, you could split it between House 2 and 3 in a way that covers your building budget for the apartment.

The thing that the gurus never tell anyone is that the majority of creative finance deals are done by investors who don't need creative financing, that is their leverage and why they can walk away, thereby making them more attractive then the one person who can only do the deal one way because they have no money of their own.

Alternatively, if you leave your paycheck in your checking account earning .01% interest, there is no real benefit.  

Take advantage of the lower downpayment programs early on and once you are tapped out of conventional loans, I would consider alternative financing. 

Any way to capitalize on this garage outside of just attracting higher rents once I move out and/or higher sales price if I decide to sell?

COVID created a chaotic spike in both the sale & rental markets, attracting even more new real estate investors.

There is a much better alternative!