A lot of folks that work this are simply brokers and will make a fee for putting you together with Kiavi or lima one..

Question: Should I collateralize the loan (if using private or hard money), or rely on roll-over loans (to maximize the lower points and 3-4% rate)?

Are you using your own money for your flips or do you have a lender/investor that funds your flips?

Even if you don't decide to keep it in the long run, it's an appreciating asset you can make money off of.

I've used the search feature on this forum but didn't have much luck.Are there any US investors, hard money lenders, or groups that invest in flips outside of the United States, specifically in Europe (Netherlands, Spain, etc.)?

Get busy making money.  

I did save some money to have as back up.

"Before borrowing money from a friend, decide which you need most".

They have stolen my money as well as hundreds of others.  

But is that worth the money?