why don’t you hear about investors using lending club or lending tree for cash money offers ?
They aren't cash. It's still a loan. That means an underwriting/screening process.
Cash is liquid hard money in the bank or in a money belt (auctions).
Even then, why don’t you hear people using them?
The money doesn't have to be seasoned so a loan like this would work. I imagine the rehabber is saying they are going to refi credit cards and uses the money for a the property. If it were me I wouldn't broadcast it.