Is an LLC overkill for this type of arrangement? 

What type of help do you need? 

You may even want to set up different entities for the different type of activities you'll be involved in to maximize tax benefits.

More specifically, where are you getting the renters from (craigslist, airbnb, vrbo, etc...) and what type of renter are you getting from these marketing sources (corporate, professors/students, traveling nurses etc...). 

@Ben Miculob  It looks like you have two different types of comps here.  

They would almost be guaranteed to lose money if the owner could not pay...The two types of sellers who are most open to Seller Financing in our experience are:- Sellers who are stuck on their sales price.   

Well, I'm not advising that someone is definitely up to no good, but if they haven't provided you with any type of comfort, peace of mind, and trust that you need just shop around as much as you can.  

What type of units are they?

I have a shop in my town that has all sorts of legal documents for $5-$10 per.2) Option agreement - You can find these also at the same type of shopThese two documents MUST be separate documents.

I think just buying a retail type property might get you the equity growth from just the overall market appreciating, which is not always a sure thing.