These sellers hand you the keys and stay out of the way until its time to sign a contract. 

You can pay a flat fee listing service a few hundred bucks to upload a listing (you'll have to answer calls, schedule showings, set up a lockbox, get a sign, vet potential buyers, avoid scammers and people trying to sell you stuff, negotiate and manage the sale yourself).

This has now been signed by the seller for over a week. 

I know DSCR could affect my DTI, maybe if I put it under a llc and sign as the guarantor could I work around it affect me personally?  

If you sign up as a client they provide legally vetted forms and can advise on the process at no charge.

Do I need to have them sign a new lease with my company name on it not changing any of the terms or do I just inform them on how to pay the rent? 

I have a signed contract.

Some have signed 2025 leases already.

For example, the signs of the 2008 housing crash were all over for everyone to see but many investors were blindsided by their "following the herd until the last minute before the party ends" kind of strategy and lost everything as a result.

Anytime you have a vacant unit, you can just sign up with whomever for a month-to-month plan and cancel when you are done.