When they return in September, they already know where they are going to live and they start the semester and the house sits vacant because you didn't put in on the market from Feb-May.

This begs the question of whether it's more profitable to do long term rental leases or short term vacation rentals or even an Airbnb setup for these properties.The main reasoning here of course is the still very depressed prices offering high potential for return.

There are many reasons I dislike investing with only cash, and it seems to me the biggest is because the return on investment is much lower than when I use leverage.

This will help you understand how the different costs, mortgage and rent can affect the return on investment.

You need to rent it for $6k/month to actually make a good return or maybe $4.5k **MINIMUM** to have it close to break even. 

2) Since the mortgage only has one person's name, can we deduct the mortgage interest in LLC's tax return instead of that person's personal tax return? 

Let's also say together we purchase a multifamily @ $1,000,000   I understand the prohibited parties issue.1) If we (myself and the SDIRA) were going to put 20% down...does that have to be in equal amounts meaning 10% from me and 10% from SDIRA and everything is split 50 / 50 or can you still have normal deal partnership flexibility...so something like the SDIRA puts in the entire 20%, owns 50% of the property but gets a "preferred return", etc.2) Perhaps the bigger question is financing, I know there is SDIRA financing that is non recourse but that is typically for 50% LTC. 

Plus another $100k in my pocket.Infinite returns (+$100k)Loan will be about $17k/month, which means it should throw off about $2k before I upgrade those last units and about $5k+ after. 

Unless you think you can make a 60% profit return on your $50k you will come out in the red. 

In return creating a tax write off for yourself.