Again I'm only 20 years old and my credit score is about 700 right now so a loan would be difficult without a co borrower.

So if the sister is completing (and not just helping) it means (1) she is going to live there or (2) she is going to be a co-signer. 

By the way, there's nothing to say that a co-signer as a value-add is (in and of itself) a "bad" thing.

So, here's my case:I have a co-living business.

I was recently laid off from my Aviation career of 10 years, just after hearing a co-worker give me an opportunity to work with him and his partner on Rehab homes.

If one of the group of roommates does not earn 3Xs the rent I require a co-signor for that individual, so incase a roomamte leaves, I know there should not be a payment issue from my viewpoint with my requirement but sure feels like many applicants who want to do this, dont seem to grasp my viewpoint.

I don't think you can own a co-op in an llc.I would go with WV personally if you can get in.Another thing with a co-op is that they might want 20% down and 18-24 months in mortgage/maintenance in escrow. 

I was informed that if I get a HML, I might need a co-signer for the amount and the lender would cover more of what they would if I didn’t have a co-signer.

An LLC might not be needed, maybe just a co-ownership agreement depending on what you have going on and your relationship with your partner. 

Sometimes it's taking care of peeling paint and slapping water heater straps on and installing a CO detector.