From your profile it seems like you haven't had much experience, and being able to manage that large of a property really does require having all your pieces in a row before you pull the trigger.

I know that "subject to" transfers the deed and might trigger the D.O.S Clause.

hi Ashley,               welcome to BP. i have been looking into fitchburg, as u know there are lots of choice for a great price but haven't been able to pull the trigger.  

Separate the deal- have regular rent payments and then an additional payment that can go to the principle if they pull the trigger. thats only a few things. there are many pit falls you can fall into without the proper paperwork at the start.

Using your current home as collateral for this deal might be triggering that fear.

Using leverage within your IRA triggers a tax called UBIT that's tied to the financed portion of the net income.  

Or can he transfer the title to my LLC without triggering "due on sale"?

In the end, no harm, no foul.This shows how important it is to be ready to pull the trigger.

Just pull the trigger!

@Fred HellerBy the way, Thanks everyone for the input I really appreciate it, I'm probably going to be asking a ton of questions now since I'm in the process of pulling the trigger finally.