One of my STRs was in an old area that had always been very lower middle class, manufactured homes scattered throughout.

Confirm that the provider has a pristine reputation (e.g.

The answer is no one who is reputable.

Focus on your reputation, not the commission. 

Reputation  has its benefits.   

This would probably help since the next one I build I could immediately put for sale and do a short term rental while it sells.I have many years of construction experience and have also done a fix and flip, in addition to building ground up construction, as well as 10 years of entrepreneurial experience running a paddle board rental company... i have a BS in Physics from Georgia Tech , a PhD in Theoretical Chemistry from UT Austin, and did Postdoctoral research using Computational Engineering where I designed, manufactured, and tested a shock mitigating metamaterial...

@Andres Rodriguez and @Srikant Puvvada Southern Impression Homes is a pretty reputable group from what I've heard, but I haven't interacted with them myself.

That comes down to the lender's reputation, skill, and willingness to get the deal done.

I was under contract but all my local lenders would not or could not loan on a manufactured home.

For illustration purposes the cheaper Delta fixtures most investors purchase at Home Depot or Lowes aren't sold at plumbing supply stores because Delta licenses these less expensive options exclusively to the big box stores (same is true for other manufacturers as well).