You're actually not doing a "flip" per se, if you are only in contract. There can be dangerous ramifications of marketing a property that you do not yet hold title to but there are ways to find buyers and lock up inventory. What you're attempting to do is actually called novation and finding the cash buyers is a harder task than many would lead you to believe.
The problem is vetting your buyer and making sure that they actually have the funds and will commit to purchasing the right to the house. I've been doing this for 20 years and I can tell you that you certainly don't want to get stuck with a bunch of contracts gone bad.
If you are truly interested in learning and understand that this is an art that takes many years to perfect, then let's chat.
There are way too many people out there trying to enter an industry at an expert level with novice knowledge and all that does it drive prices down and stall growth in the area.