The answer is yes, 2nd lien DSCR loans exist and more than one lender can do them, but you would probably have to up your credit score to be able to get up to a total of 75% ltv between 1st and second lienOtherwise, you would have to get lucky on a favorable appraisal.

What documents do they require, what credit scores do they allow, how do they verify previous rental history, etc.?

What I like about them is you can also get carbon copy forms which is what we use or you can download them to get electronic PDF versions. 

•Continue building your Paydex Score (80+) and Experian Intelliscore.4.Leverage Credit to Access Funding:•Once you’ve established some business credit history, work with a business funding specialist to secure $50K–$250K in lines of credit.

Backstory: 22 years old about to get out of military after first contract. 70k cash saved up & 775 credit score, no debt.

They even emailed me a draft version of the lawsuit they are “planning” to file. 

DSCR loans are based off of down payment, credit score and either actual or market rents so it helps to supercharge an investor's real estate goals and net worth.

We have credit scores over 730 and have been "soft approved" for around $750k. 

The website 51west.properties also scores low on scam advisor ("owner is using a service to hide their identity, high number of suspicious websites on the server, registrar has a high % of spammers and fraud sites, website is (very) young, website appears to be hosted by a company with a bad reputation", all according to https://www.scamadviser.com/check-website/51west.properties...)Trust your instincts. 

And they said it's okay to "temporarily" have a bad credit score because you could also repair your credit.