Therefore I do not have the minimum 2 year established business history which some loans that offer a low down payment may require.  

You can also use sales history in Zillow as a secondary source, but forget Zestimate.Your question about your current lenders subordinating their loans, that will not happen.You seem to be looking for a commercial line of credit from the bank, leveraging off of your free & clear property.

I have been kind of stalled because I found out I don't have any credit history in the U.S.

But more than likely given the original tenants history with late rent I don't think I would have cut them any deal and just ask them to leave or evicted them on late rent.Bottom line - If you KNOW someone new is moving in get them on the lease BEFORE they move in even a toothbrush!

Do you have a bite history and a letter from the vet signed saying they were given all appropriate vaccinations and spayed and neutered??

We also make it clear that we value open and honest communication, so if they have a weakness in rental history, legal history, credit history, or income history... it is best to be upfront about it as we may be able to work with them.

Sometimes candidates have histories of lawsuits.

If you CAN'T show Lenders a history of GREAT investments, maybe it's time to divest yourself of those "mistakes", first?

Put all tenants on the lease, responsible jointly and severally if they are first time renters or college age, get moms and dads to guarantee the lease, because they won't have rental histories and probably not sufficient credit.You might ask if they would all like to move in July or August!

Some will have zero history with a high cap rate marketed which by itself is at best misleading.Also consider sfrs were not designed as investments as much as they were designed to be lived in.