I know people like LLCs for liability protection however having discussed with a couple of attorneys I cannot get a clear answer on how much if any extra protection you get over a good insurance policy. On the down side, you cannot get a conforming loan as an LLC and you have to transfer the title later. This may or may not be okay with your bank. Secondly, it creates a lot more paperwork and expense to track. For just a few properties it may not be worth it.
Regarding SDIRA, its not the optimum way to buy a house. Again, complicated paperwork, complex rules (you cannot do any work on it yourself, cannot ever occupy it, all expenses must be paid from IRA etc) and your net tax benefit is small if you consider depreciation, mortgage interest etc that you can take outside the IRA. An SDIRA is a good place to put high yielding passive investments like trust deeds etc. Also not sure how easy to get a conforming loan that way either.
For my investments so far, I buy in my own name put $300K liability insurance on each home and have a $1M umbrella policy. My attorney seems to think thats a reasonable protection. I may rethink the LLC option if I learn something new.