@Vincent Park
Have you decided where you want to invest? Or will you be deciding based on your criteria? Do you have an end goal like # of units or total amount / return? Before you buy, think about what you want to get out of the investment. As @Jay Hinrichs said, it may not be the time to get cash flow and appreciation play now so you may need to go the non-turnkey route if that's what you're looking for.
When I started looking into Memphis, I first found MI online and attended their event and reviewed their property proforma info. After analyzing quite a few properties, I decided not to invest with them. Other than the potential appraisal issue, I didn't like the return when I plug in with my own assumptions...
I have not worked with Norada or JWB before so I can't comment on them.
By the way, I think minimum down payment is 20% for investor loan. You get slightly better interest rate if you put down 25%. Closing cost varies because each state / city has different property tax rate and insurance premium - but I think people use roughly 4% based on $100K purchase price.
Good luck!
Henry