Private money and when to make an offer on a BRRR

[Rivers Ford]

So I've found a great property to purchase that will be our first investment. This property is perfect for a BRRRR and I actually have a connection with a private money lender. I'm meeting a contractor at the property tomorrow to get some more firm numbers. My question is when do I make the offer? Will I need to secure my finances first or get it under contract first? Has anyone ever made a "cash" offer contingent on financing? That really seems like an oxymoron.... I also do not want to jerk the private money lender around because he could be key in future deals as well. What have you guys experiences been?