While this could get very costly with traditional LLCs, executing this method with a Series LLC is much quicker and more cost effective.

If your IRA is owner of LLC you are not a human owner of record.

You are correct however, finding a lender for mobile homes can be difficult, and most traditional banks will not touch them

For example, maintenance is traditionally going to average 10% of your gross income but you've only calculated 7.5%.

I know non-resident mortgages are pretty much non-existent (actually, mortgages are traditionally less common in CR). 

I may consider a traditional value add with a select few sponsors.  

Additionally, the super low down payment and powerful strategy somewhat rationalizes paying more for the property than a traditional homebuyer or investor.

I want to know what is the benefit to obtaining  a property under this type of mortgage vs. doing a traditional conventional mortgage and financing the renovations by other methods (ex: hard money or personal loan). 

Some RE options in order of passivity (IMO) from most active to most passive: New development, Flip, BRRRR, STR without PM, traditional buy and hold without PM, STR with PM, traditional buy and hold with PM, full service turnkey, Commercial MF with PM, Commercial non residential, NNN, syndication, REIT. 

So basically it's not a pure analysis of STRs vs other asset classes but more like traditional residential real estate investments whether long term buy and holds or true STRs.