There are some shops and wholesalers that investors will avoid like the plague.

There are many ways to do this and many potential lead sources to consider.With MLS access, you can look up expired listings and call up those homeowners.

I dont know what they charge to be listed as lender or an agent..

Something as simple as not having blackout curtains can make or break a listing. 

I actually furnished all the rooms already back when I bought the house, so I've been trying to list my rooms on Airbnb.

Lenders are always competing so shop around.  

Once we have a completed application, we verify income (by calling the employer and/or with paystubs), verify previous address history (this will show up on the credit check, we ask about any addresses that show up on the credit check but are not listed on their application), and verify identity by requesting a copy of their photo ID to make sure their info matches the application and screening reports.Next, we run credit, criminal, and eviction reports.

Some first time home buyer with overoptimistic DIY skills and a gross underestimation of how to fit 500 man hours of rehab into a few weekends will pay list price. 

They will work for you for "free" on the purchase and you will eventually need a rock star when listing your flip.

Definitely shop around for some options as well!