Interesting,  In any other business, if I have resale tax license, I don't pay tax on things I'm buying to resell only collect sales tax when I sell. 

I believe there's a minimum if they're following Fannie Mae guidelines, basically going to resell your loan, so just find a lender who services their own loans.

You can resell the day you buy it if your buyer is using cash to purchase.

If I was wanting a quick value-add to turn around and resell or refinance I would move the tenants out as soon as their leases allowed.

Your intent in purchasing the property was primarily to resell it.  

If your rates are not at market you are devaluing your investment property, except in the case of SFHs which will resell at a higher rate if there is no tenant in place at time of sale. 

Does $10k Rehab (new appliances, restoration of exterior, new bathroom fixtures, etc) mean $10k higher resell price?

You will have to be confident in your ability to resell the place for them to accept a contingency, however, or else it is not worth it to them to tie the house as pending, when they could be marketing it for sale to another buyer who is buying it directly. 

If you have a pile of cash and patience, I think you could probably close some deals and resell them for a reasonable profit.

But by doing this they were able to purchase these homes and then resell them on contract.